Selenoprotein-Driven Antioxidant Enzyme Network: GPX, TXNRD, and Redox Homeostasis Research

The core of selenoprotein research is to clarify how redox reactions involving selenocysteine affect antioxidant defense, mitochondrial homeostasis, inflammatory responses, and cell death. Combined detection of selenoproteins such as GPX, TXNRD, and SELENOP with SOD, CAT, PRDX, GSH/GSSG, ROS, and lipid peroxidation markers can provide a more complete evaluation of oxidative stress status.

Keywords: selenoproteins; antioxidant enzymes; glutathione peroxidase; thioredoxin reductase; GPX; TXNRD; SELENOP; oxidative stress; ROS; GSH/GSSG; lipid peroxidation

1 Core Questions in Selenoprotein and Antioxidant Enzyme Research

1.1 Research targets

(1) Selenium-containing antioxidant enzymes

GPX and TXNRD are the most representative selenium-containing antioxidant enzymes. Their active centers contain selenocysteine, and their reaction efficiency and reducing capacity are generally higher than those of corresponding sulfur-containing structures. GPX mainly participates in the clearance of hydrogen peroxide, lipid peroxides, and organic peroxides. TXNRD maintains protein disulfide bonds, peroxiredoxins, and cellular redox signaling by reducing thioredoxin.

(2) Selenium transport and selenium homeostasis proteins

SELENOP is an important selenoprotein involved in selenium transport in plasma and tissues and can affect tissue selenium supply and downstream selenoenzyme expression. SELENOS, SELENOK, SELENOT, and other selenoproteins are more involved in endoplasmic reticulum stress, inflammatory regulation, calcium homeostasis, and protein quality control. In selenoprotein network studies, total selenium alone should not be the only measurement; selenoprotein expression and enzyme activity changes should also be included.

(3) Non-selenium-dependent antioxidant enzymes

SOD, CAT, PRDX, GSR, and GST are not typical selenoproteins, but they are closely coupled with the selenoprotein antioxidant system. SOD catalyzes the dismutation of superoxide anions, CAT decomposes hydrogen peroxide, PRDX clears peroxides through the thioredoxin system, and GSR maintains the GSH/GSSG cycle. Measuring only GPX or TXNRD is insufficient for fully assessing antioxidant defense status.

1.2 Research objectives

(1) Assess selenium-dependent antioxidant capacity

If the focus is selenium nutrition, selenium supplementation, selenium deficiency, or selenium toxicity, GPX activity, TXNRD activity, SELENOP level, total selenium, or selenium speciation should be prioritized, together with GSH/GSSG, ROS, and lipid peroxidation markers.

(2) Elucidate oxidative stress mechanisms

In disease models, drug-induced injury, inflammation, or cell death studies, selenoproteins should be analyzed within the redox network. Decreased GPX4 accompanied by increased lipid ROS and MDA/4-HNE often suggests impaired lipid peroxidation defense. TXNRD inhibition accompanied by reduced PRDX reduction capacity is more indicative of thioredoxin system imbalance.

(3) Distinguish expression changes from functional changes

Increased mRNA does not necessarily mean increased enzyme activity, and increased protein expression does not necessarily indicate enhanced antioxidant function. Selenoprotein translation depends on the selenocysteine insertion mechanism and is affected by selenium supply, SECIS structure, SBP2, tRNA[Sec], and cellular stress status. Therefore, selenoprotein research should simultaneously consider transcriptional, protein, and enzymatic activity levels.

Table 1 Rapid Selection Pathway for Selenoprotein and Antioxidant Enzyme Research

Research Question	Priority Markers	Supporting Markers	Interpretation Focus
Selenium deficiency or selenium supplementation effect	Total selenium, SELENOP, GPX activity, TXNRD activity	GSH/GSSG, MDA, ROS	Determine whether selenium supply is translated into antioxidant enzyme function
Lipid peroxidation and ferroptosis	GPX4, lipid ROS, MDA, 4-HNE	GSH, ACSL4, SLC7A11	GPX4 decline should be interpreted together with lipid peroxidation readouts
Mitochondrial oxidative stress	GPX1/4, TXNRD2, SOD2	Mitochondrial ROS, membrane potential, ATP	Distinguish changes in mitochondrial ROS generation and clearance capacity
Inflammation and ER stress	SELENOS, SELENOK, SELENOT	IL-1β, TNF-α, CHOP, GRP78	Focus on the relationship between selenoproteins and inflammation/protein-folding stress
Drug or toxic injury	GPX, TXNRD, SOD, CAT	ROS, MDA, LDH, cell viability	Determine whether oxidative injury is accompanied by antioxidant system depletion
Antioxidant evaluation in animal models	Tissue selenium, GPX, TXNRD, SOD, CAT	Histopathology, serum biochemistry	Tissue specificity is more important than a single serum marker

2 Key Selenoproteins and Their Antioxidant Functions

2.1 Glutathione peroxidase family

(1) GPX1

GPX1 is mainly distributed in the cytoplasm and mitochondrial matrix and is responsible for clearing hydrogen peroxide and some organic peroxides. When GPX1 activity decreases, cells become more sensitive to H₂O₂ burden, which is commonly seen in selenium deficiency, oxidative stress models, and some metabolic abnormalities. GPX1 analysis should be combined with total GPX activity, GSH levels, and H₂O₂-related readouts to avoid interpreting functional changes based only on protein expression.

(2) GPX2

GPX2 is important in the gastrointestinal epithelium and participates in mucosal barrier antioxidant defense and peroxide clearance under inflammatory conditions. In intestinal inflammation, intestinal epithelial injury, intestinal tumors, and oxidative stress models, GPX2 changes show tissue specificity. For intestinal tissue samples, GPX1 detection alone should be avoided without considering GPX2.

(3) GPX3

GPX3 is a secreted glutathione peroxidase commonly present in plasma and the extracellular environment. Its changes can reflect body fluid antioxidant capacity, kidney-derived secretion regulation, and systemic oxidative stress status. When detecting GPX3 in serum or plasma samples, sample hemolysis, protein concentration, and total selenium level should be considered.

(4) GPX4

GPX4 is a core selenoprotein in lipid peroxidation defense and ferroptosis research and can directly reduce membrane phospholipid hydroperoxides. GPX4 reduction or inactivation is often associated with increased lipid ROS, MDA, 4-HNE, and membrane lipid injury. In ferroptosis research, GPX4 should not be interpreted alone; it should be evaluated together with GSH depletion, SLC7A11 changes, ACSL4, iron loading, and lipid peroxidation probe results.

2.2 Thioredoxin reductase family

(1) TXNRD1

TXNRD1 is mainly located in the cytoplasm, maintains thioredoxin in its reduced state, and participates in peroxide reduction, DNA synthesis, transcription factor regulation, and redox signal transduction. When TXNRD1 is inhibited, cells may show protein disulfide accumulation, blocked PRDX cycling, and abnormal redox signaling.

(2) TXNRD2

TXNRD2 is mainly localized in mitochondria and is a key enzyme in the mitochondrial thioredoxin system. When mitochondrial ROS increases, membrane potential decreases, or respiratory chain stress occurs, TXNRD2 should be prioritized. Detecting only total TXNRD activity may mask subtype-specific mitochondrial changes. If necessary, mitochondrial fractions or subtype-specific antibodies should be used.

(3) TXNRD3

TXNRD3 is highly expressed in specific tissues and is associated with sperm development and thioredoxin/glutaredoxin-related functions. In reproductive system oxidative stress research, TXNRD3 is more targeted than conventional TXNRD1.

2.3 Selenium transport and stress-related selenoproteins

(1) SELENOP

SELENOP contains multiple selenocysteine sites and is an important indicator of plasma selenium transport and tissue selenium supply. Decreased serum SELENOP may indicate insufficient selenium transport, but it does not necessarily mean that all tissue selenoprotein activities are reduced. Hepatic synthetic capacity, inflammatory status, and nutritional conditions can all affect SELENOP levels.

(2) SELENOS

SELENOS is often associated with endoplasmic reticulum-associated degradation, inflammatory responses, and protein quality control. In inflammatory models, changes in SELENOS can be analyzed together with TNF-α, IL-6, CHOP, GRP78, and other markers to determine whether selenoproteins are involved in the coupling between endoplasmic reticulum stress and inflammation.

(3) SELENOK and SELENOT

SELENOK is associated with immune cell function, calcium flux, and endoplasmic reticulum membrane-related processes. SELENOT is related to cellular protection, calcium homeostasis, and secretory function. These two proteins are not usually used as basic antioxidant enzyme activity markers, but they have extended value in immune, endocrine, and neuroprotective research.

Table 2 Functional Positioning and Detection Focus of Representative Selenoproteins

Selenoprotein	Main Localization	Key Function	Recommended Detection Level	Interpretation Focus
GPX1	Cytoplasm, mitochondria	Clears H₂O₂ and organic peroxides	Enzyme activity, protein, mRNA	Combine with GSH, ROS, and H₂O₂ readouts
GPX2	Gastrointestinal epithelium	Mucosal barrier antioxidant defense	mRNA, protein	Pay attention to tissue specificity
GPX3	Extracellular environment, plasma	Body fluid antioxidant defense	ELISA, enzyme activity	Pay attention to plasma sample quality and hemolysis
GPX4	Cell membrane, mitochondria, nucleus-related compartments	Lipid peroxide reduction, ferroptosis defense	Protein, enzyme activity, lipid ROS	Combine with GSH and lipid peroxidation markers
TXNRD1	Cytoplasm	Thioredoxin system reduction	Enzyme activity, protein, mRNA	Focus on PRDX cycling and redox signaling
TXNRD2	Mitochondria	Mitochondrial antioxidant defense	Subcellular protein, enzyme activity	Combine with mitochondrial ROS and membrane potential
SELENOP	Plasma, liver-derived secretion	Selenium transport and tissue selenium supply	ELISA, total selenium	Does not equal all selenoenzyme activities
SELENOS	Endoplasmic reticulum	ER stress, inflammatory regulation	Protein, mRNA	Combine with CHOP, GRP78, and inflammatory cytokines

3 Combined Analysis of the Antioxidant Enzyme Network

3.1 GPX system and glutathione cycle

(1) GSH supply

GPX requires GSH as an electron donor when catalyzing peroxide reduction, generating GSSG after the reaction. If GSH is depleted, peroxide clearance capacity may decrease even when GPX protein expression is not low. Therefore, GPX studies should simultaneously detect GSH, GSSG, and the GSH/GSSG ratio.

(2) GSR regeneration capacity

GSR reduces GSSG back to GSH and maintains the glutathione cycle. If GSR activity is insufficient, GSSG accumulation limits sustained GPX reactions. In drug injury, mitochondrial stress, and nutritional deficiency models, GPX activity should be interpreted together with GSR and NADPH supply.

(3) GPX4 and ferroptosis

GPX4 depends on GSH to clear lipid peroxides. When SLC7A11 decreases and cysteine import is limited, GSH synthesis is restricted, affecting GPX4 function. In ferroptosis research, GPX4, GSH, lipid ROS, and iron metabolism markers should be placed within the same interpretation framework.

3.2 TXNRD system and peroxiredoxin cycle

(1) TXN/TXNRD axis

TXNRD uses NADPH to reduce thioredoxin, which then participates in PRDX reduction, protein disulfide regulation, and redox signaling. When TXNRD is inhibited, PRDX may remain oxidized, H₂O₂ clearance may decrease, and cellular redox signaling may be enhanced.

(2) Functional division between PRDX and GPX

Both PRDX and GPX can process peroxides, but their electron donors differ. GPX depends on GSH, whereas PRDX depends on the TXN system. If only GPX is measured, compensation or imbalance in the TXNRD-PRDX axis may be missed. If only TXNRD is measured, it is still impossible to determine whether the GSH system can maintain antioxidant capacity.

(3) NADPH supply

Both the GSH and TXN systems ultimately depend on NADPH to maintain reducing power. When NADPH sources such as glucose-6-phosphate dehydrogenase, malic enzyme, and isocitrate dehydrogenase are impaired, both GPX and TXNRD functions may decline. In metabolic stress models, NADPH/NADP⁺ or related metabolic pathways should be considered.

3.3 Complementary relationship among SOD, CAT, and selenoproteins

(1) SOD provides upstream conversion

SOD converts superoxide anions into hydrogen peroxide. If SOD activity increases while GPX or CAT is insufficient, H₂O₂ may accumulate and enhance oxidative pressure. Therefore, increased SOD should not be simply interpreted as enhanced antioxidant capacity.

(2) CAT and GPX share H₂O₂ clearance

CAT efficiently decomposes H₂O₂ mainly in peroxisomes, whereas GPX has broader peroxide-processing capacity in the cytoplasm, mitochondria, and membrane lipid environments. When tissue hydrogen peroxide burden is high, the relative contributions of CAT and GPX should be interpreted according to subcellular localization.

(3) Comprehensive interpretation is better than single-marker interpretation

The antioxidant enzyme network is compensatory. An increase in one enzyme may indicate enhanced defense, but it may also represent stress induction. To assess redox status, multiple markers among ROS, MDA or 4-HNE, GSH/GSSG, GPX, TXNRD, SOD, and CAT should be combined.

Table 3 Marker Combinations in the Selenoprotein Antioxidant Network

Module	Core Markers	Supporting Markers	Interpretation Focus
Glutathione system	GPX1/GPX4, GSH, GSSG	GSR, SLC7A11, NADPH	Determine whether GSH supply matches GPX function
Thioredoxin system	TXNRD1/2, TXN, PRDX	NADPH, oxidized PRDX	Determine whether the TXN-PRDX cycle is blocked
Superoxide anion clearance	SOD1, SOD2, SOD3	Mitochondrial ROS, H₂O₂	Increased SOD should be interpreted together with downstream H₂O₂ clearance
Hydrogen peroxide clearance	GPX, CAT, PRDX	H₂O₂, total ROS	Distinguish cytoplasmic, mitochondrial, and peroxisomal contributions
Lipid peroxidation	GPX4, MDA, 4-HNE	Lipid ROS, iron ions, ACSL4	Determine whether ferroptosis-related oxidative injury exists
Selenium supply	Total selenium, SELENOP	GPX activity, TXNRD activity	Determine whether selenium nutrition is converted into selenoenzyme function

4 Detection Methods and Experimental Design

4.1 Enzyme activity detection

(1) GPX activity detection

GPX activity detection is usually based on GSH consumption, GSSG formation, or absorbance changes in a GSR/NADPH-coupled system. Total GPX activity can reflect overall peroxide clearance capacity, but it cannot distinguish GPX1, GPX3, and GPX4. If ferroptosis is being studied, GPX4 protein, GPX4 activity, or lipid peroxidation readouts should be prioritized for combined interpretation.

(2) TXNRD activity detection

TXNRD activity is often detected by reducing DTNB or specific substrates to generate measurable signals. Since other reductases may also reduce some substrates, inhibitor controls or blank subtraction should be included. To distinguish TXNRD1 from TXNRD2, total activity alone is insufficient; subcellular fractionation or subtype-specific detection is required.

(3) SOD, CAT, and GSR activity

SOD, CAT, and GSR activities can supplement antioxidant network information. SOD reflects superoxide anion processing capacity, CAT reflects H₂O₂ decomposition capacity, and GSR reflects GSH regeneration capacity. Combined detection with GPX and TXNRD can prevent overinterpretation caused by a single marker.

4.2 Protein and transcription detection

(1) qPCR

qPCR is suitable for detecting gene expression of GPX1, GPX4, TXNRD1, TXNRD2, SELENOP, SELENOS, and other genes. Transcriptional changes in selenoproteins may indicate regulatory direction but cannot replace enzyme activity. Under selenium deficiency, some selenoprotein mRNAs may not change significantly, while protein translation and enzyme activity are already affected.

(2) Western blot

Western blot can detect selenoprotein expression and specific subtype changes. GPX4, TXNRD1, TXNRD2, SELENOP, and SELENOS are suitable for protein-level validation. Membrane proteins, secreted proteins, and mitochondrial proteins require appropriate lysis conditions and loading controls.

(3) ELISA

ELISA is suitable for detecting serum SELENOP, GPX3, or specific proteins in tissue homogenates. In serum samples, hemolysis, freeze-thaw cycles, and lipemic interference should be controlled. ELISA-detected concentration does not equal enzyme activity, especially because inactive or oxidatively modified proteins may still be recognized by antibodies.

4.3 Oxidative stress readouts

(1) ROS detection

Total ROS probes are suitable for initial screening but have limited specificity. Mitochondrial ROS, lipid ROS, and H₂O₂ should be measured using corresponding probes or detection systems. In selenoprotein research, ROS results should be interpreted together with GPX, TXNRD, and antioxidant metabolism indicators.

(2) Lipid peroxidation detection

MDA, 4-HNE, and lipid ROS can be used to evaluate membrane lipid oxidative damage. In GPX4-related studies, lipid ROS is more targeted than total ROS. Increased MDA suggests enhanced lipid peroxidation, but it is also easily affected by sample handling and detection method.

(3) Reducing power detection

GSH/GSSG, NADPH/NADP⁺, and total antioxidant capacity can reflect cellular reducing status. If GPX or TXNRD expression increases while GSH or NADPH decreases, the antioxidant system may be in a compensatory stress state rather than truly enhanced function.

5 Sample Types and Detection Boundaries

5.1 Cell samples

Cell samples are suitable for mechanistic validation. Selenium supplementation, selenium deficiency, gene knockdown, inhibitor treatment, or oxidative stress induction can be used to observe selenoprotein changes. Cell viability should be detected simultaneously, because severe cell death may distort ROS, MDA, and enzyme activity results. Mitochondria-related studies should distinguish total cell lysates from mitochondrial fractions.

5.2 Animal tissues

Animal tissues show clear organ differences. The liver is an important organ for selenium metabolism and SELENOP synthesis. The kidney is also sensitive to GPX3 and selenium metabolism. Myocardium and brain tissue are more focused on mitochondrial oxidative stress. Absolute enzyme activities should not be directly compared across different tissues; normalization by protein concentration, tissue weight, or cell number is required.

5.3 Serum and plasma

Serum/plasma is suitable for detecting systemic markers such as total selenium, SELENOP, GPX3, MDA, and total antioxidant capacity. Hemolysis releases erythrocyte antioxidant enzymes and affects GPX, SOD, and MDA detection, and improper sample handling can cause obvious deviation. If tissue oxidative stress is being evaluated, serum results should be combined with target-organ tissue detection.

5.4 Clinical or disease samples

Clinical samples are often affected by age, nutritional status, liver and kidney function, inflammation, medication, and underlying disease. Confounding factors should be considered when interpreting selenoprotein markers. A single serum selenium level or single GPX activity is insufficient for determining disease mechanisms and is better combined with pathological, inflammatory, metabolic, and oxidative injury markers for modeling.

Table 4 Key Points for Detecting Selenoproteins and Antioxidant Enzymes in Different Samples

Sample Type	Suitable Markers	Main Risk	Control Strategy
Cell lysate	GPX, TXNRD, GSH/GSSG, ROS	Cell death distorts enzyme activity and ROS	Detect cell viability and protein concentration simultaneously
Mitochondrial fraction	TXNRD2, GPX4, SOD2, mitochondrial ROS	Insufficient fraction purity	Verify using mitochondrial and cytosolic markers
Liver tissue	SELENOP, GPX1, TXNRD1, total selenium	Tissue heterogeneity and lipid interference	Fix sampling site and normalize by protein
Kidney tissue	GPX3, GPX1, oxidative injury markers	Blood residue affects results	Perfuse or standardize tissue collection
Myocardial tissue	GPX4, TXNRD2, SOD2, MDA	Ischemia and sampling time affect oxidative readouts	Process rapidly at low temperature and unify sampling time
Serum/plasma	SELENOP, GPX3, total selenium, MDA	Hemolysis, freeze-thaw, and lipemia	Exclude hemolyzed samples and reduce freeze-thaw cycles
Clinical samples	SELENOP, GPX, TXNRD, inflammatory markers	Nutritional and disease confounding	Perform stratified analysis and add supporting markers

6 Common Result Patterns and Interpretation

6.1 GPX increases after selenium supplementation, but ROS does not decrease

Increased GPX indicates that the selenium-dependent antioxidant system may be activated, but unchanged ROS suggests that oxidative sources remain strong or that TXNRD, CAT, SOD, GSH/NADPH supply has not improved simultaneously. GSH/GSSG, TXNRD activity, mitochondrial ROS, and MDA should be measured to identify the limiting step.

6.2 GPX4 decreases with increased lipid ROS

This pattern suggests impaired lipid peroxidation defense and is commonly used in ferroptosis-related studies. If GSH decreases, SLC7A11 decreases, ACSL4 increases, or iron load increases at the same time, the ferroptosis direction is further supported. If only GPX4 decreases but lipid ROS does not change, the functional significance of protein expression changes should be considered.

6.3 TXNRD activity decreases but TXNRD protein increases

Increased protein may reflect compensatory expression, while decreased activity may result from insufficient selenium supply, active-site damage, oxidative modification, or inhibitor action. TXN redox status, PRDX oxidation level, NADPH supply, and total cellular selenium should be measured simultaneously.

6.4 SELENOP decreases but tissue GPX shows no obvious change

Decreased SELENOP suggests changes in selenium transport or liver-derived secretion, but tissue selenoproteins may have prioritization and retention mechanisms. Some tissues may maintain key GPX or TXNRD expression. Tissue total selenium, GPX activity, TXNRD activity, and tissue-specific selenoprotein expression should be further detected.

Table 5 Common Abnormal Patterns in Selenoprotein and Antioxidant Enzyme Research

Result Pattern	Possible Explanation	Recommended Additional Tests
GPX activity decreases, GSH decreases, MDA increases	Glutathione system depletion and enhanced lipid peroxidation	GSR, NADPH, GPX4, lipid ROS
GPX4 decreases, lipid ROS increases	Impaired lipid peroxidation defense and increased ferroptosis risk	SLC7A11, ACSL4, iron ions, 4-HNE
TXNRD decreases, PRDX oxidation increases	Insufficient reducing capacity of the thioredoxin system	TXN redox status, NADPH
SOD increases, H₂O₂ or MDA increases	Upstream superoxide clearance increases but downstream peroxide processing is insufficient	GPX, CAT, PRDX, GSH/GSSG
SELENOP decreases, total selenium decreases	Insufficient selenium supply or transport	GPX activity, TXNRD activity, tissue selenium
Antioxidant enzymes increase but cell injury worsens	Compensatory stress response, not necessarily successful protection	ROS, LDH, cell viability, apoptosis/necrosis markers

7 Key Control Points in Experimental Design

7.1 Selenium treatment concentration

Selenium supplementation experiments should distinguish nutritional supplementation from toxic dosage. Low-dose selenium can promote selenoprotein synthesis, whereas excessive doses may induce oxidative stress, cytotoxicity, or metabolic disorder. Different selenium forms, such as sodium selenite, selenomethionine, methylselenocysteine, and nano-selenium, differ in cellular uptake and conversion efficiency into selenoproteins, and should not be considered equivalent simply based on elemental selenium concentration.

7.2 Time gradients

Selenoprotein expression, enzyme activity recovery, and oxidative damage improvement occur over different time scales. mRNA changes may precede protein changes, and protein changes may precede functional recovery. Multiple time points are recommended to avoid drawing conclusions from a single endpoint.

7.3 Positive and negative controls

Oxidative stress models should include oxidative induction controls, antioxidant intervention controls, and selenium treatment controls. Ferroptosis studies may include GPX4 inhibition, iron chelation, lipid antioxidant, and related controls. TXNRD studies may include TXNRD inhibitors or thioredoxin system-related controls.

7.4 Normalization methods

Enzyme activity results should be normalized by protein concentration, cell number, or tissue weight. ROS and fluorescent probe results should control cell density, probe incubation time, and instrument parameters. For serum samples, hemolysis, freeze-thaw cycles, and blood collection conditions should be recorded.

8 Product Selection for Selenoprotein and Antioxidant Enzyme Research

Table 6 Product Selection for Core GPX/TXNRD and Selenoprotein Research

Application Scenario	Cat. No.	Product Name	Grade/Specification	Application Positioning
GPX1 protein validation	Ab105709	Recombinant Glutathione Peroxidase 1 Antibody	Recombinant, ExactAb™, validated, high performance, see COA	Used for Western blot, IHC, or IF detection of GPX1 expression; suitable for cytoplasmic and mitochondrial peroxide clearance research
GPX4 protein validation	Ab105733	Recombinant Glutathione Peroxidase 4 Antibody	ExactAb™, validated, recombinant, 0.5 mg/mL	Used for GPX4 expression detection; suitable for lipid peroxidation and ferroptosis research
GPX4 protein/standard	rp220388	Recombinant Human Glutathione Peroxidase 4 Protein	Carrier-free, His-tag, ≥90% (SDS-PAGE), see COA	Used for GPX4 antibody evaluation, positive control, and GPX4 functional research
GPX2 protein validation	Ab105715	Recombinant Glutathione Peroxidase 2/GPX2 Antibody	Recombinant, ExactAb™, validated, see COA	Used for GPX2 expression detection in intestinal epithelium, barrier antioxidant defense, and inflammation-related studies
GPX4 protein validation	Ab327014	Recombinant Glutathione Peroxidase 4 Antibody	KD Validation	Used for protein validation in GPX4 knockdown, ferroptosis induction, and lipid ROS models
GPX2 protein validation	Ab330599	Recombinant Glutathione Peroxidase 2/GPX2 Antibody	Recombinant, ExactAb™, azide-free, validated, carrier-free, see COA	Used for GPX2 protein validation and immunodetection in azide-free systems
GPX3 protein/standard	rp192121	Recombinant Human Glutathione Peroxidase 3/GPX3 Protein	Carrier-free, His-tag, ≥90% (SDS-PAGE), expressed in E. coli; see COA	Used for GPX3 assay validation, positive control, and method development
Total GPX functional validation	G1374092	Glutathione Peroxidase (GPX)	Bioactive, recombinant, ActiBioPure™, high performance, EnzymoPure™, ≥90% (SDS-PAGE), ≥100 U/mg enzyme powder; ≥300 U/mg protein	Used for GPX activity system establishment, positive control, and enzymatic reaction validation
GPX1 expression intervention	G1473358	GPX1 Human Pre-designed siRNA Set A		Used for GPX1 knockdown to validate selenium-dependent peroxide clearance function
GPX2 expression intervention	G1486347	GPX2 Human Pre-designed siRNA Set A		Used for GPX2 knockdown; suitable for intestinal epithelial antioxidant and inflammation models
GPX3 expression intervention	G1473914	GPX3 Human Pre-designed siRNA Set A		Used for GPX3 knockdown; suitable for secreted GPX and body fluid antioxidant research
GPX4 expression intervention	G1491190	GPX4 Human Pre-designed siRNA Set A		Used for GPX4 knockdown to establish lipid peroxidation and ferroptosis-sensitive models
GPX5 expression intervention	G1474429	GPX5 Human Pre-designed siRNA Set A		Used for GPX5-related reproductive system or tissue-specific GPX research
GPX6 expression intervention	G1466972	GPX6 Human Pre-designed siRNA Set A		Used for GPX6 expression regulation and GPX family extension studies
GPX7 expression intervention	G1471777	GPX7 Human Pre-designed siRNA Set A		Used for ER-related GPX7 function and oxidative folding environment research
GPX8 expression intervention	G1487098	GPX8 Human Pre-designed siRNA Set A		Used for GPX8 knockdown and endoplasmic reticulum redox homeostasis research
GPX3 negative control sample	P746509	pLenti-GPX3-sgRNA		Used for GPX3 antibody validation, protein detection negative control, and method confirmation
GPX3 transcriptional control sample	P746510	pLenti-GPX3-sgRNA		Used for GPX3 qPCR validation and transcription-level negative control
GPX4 functional activation	G1424411	GPX4 activator 1		Used for GPX4 functional activation, lipid peroxidation defense, and ferroptosis protection mechanism studies
GPX4 functional activation	G1424743	GPX4 activator 2		Used for studies on GPX4 activity enhancement mechanisms
GPX4 functional inhibition	G1496676	GPX4-IN-2	Moligand™, 10 mM in DMSO	Used for GPX4 inhibition, lipid peroxidation accumulation, and ferroptosis models
GPX4 functional inhibition	G1425057	GPX4-IN-2	≥98%	Used for GPX4 inhibitor powder-form experiments and dose-response studies
GPX4 functional inhibition	G646321	GPX4-IN-3	≥99%	Used for GPX4 functional blockade and ferroptosis sensitivity validation
GPX4 functional inhibition	G654539	GPX4-IN-3	10 mM in DMSO	Used for cell treatment and GPX4 inhibition model establishment
GPX4 functional inhibition	G1497635	GPX4-IN-4	Moligand™, 10 mM in DMSO	Used for GPX4 inhibition, lipid ROS increase, and ferroptosis pathway validation
GPX4 functional inhibition	G1425056	GPX4-IN-4	≥98%	Used for GPX4 inhibitor condition optimization
GPX4 functional inhibition	G1498112	GPX4-IN-5	Moligand™, 10 mM in DMSO	Used for GPX4-related lipid peroxidation models
GPX4 functional inhibition	G1424748	GPX4-IN-5	≥99%	Used for GPX4 inhibitor powder-form experiments
GPX4 functional inhibition	G1424671	GPX4-IN-6	≥99%	Used for GPX4 inhibition and ferroptosis mechanism comparison
GPX4 functional inhibition	G1498113	GPX4-IN-6	Moligand™, 10 mM in DMSO	Used for cellular ferroptosis induction and dose-response experiments
GPX4 degradation	P1424746	PROTAC GPX4 degrader-1	≥99%	Used for GPX4 protein degradation, lipid peroxidation, and ferroptosis mechanism research
GPX4 degradation	P1424509	PROTAC GPX4 degrader-2		Used for GPX4-targeted degradation models and functional validation
GPX4 degradation	P1424469	PROTAC GPX4 degrader-3		Used for GPX4 protein-level regulation and ferroptosis mechanism research
GPX4 inhibition/ferroptosis induction	R302648	RSL3	Moligand™, ≥98%	Used for GPX4 inactivation, lipid ROS accumulation, and positive ferroptosis models
GPX1 ELISA detection	EJ1514953	Human Glutathione Peroxidase 1 (GPX1) ELISA Kit	BioReagent	Used for detecting GPX1 protein levels in human samples
GPX4 ELISA detection	EJ1514955	Human Glutathione Peroxidase 4(GPX4) ELISA Kit	BioReagent	Used for human GPX4 quantification; suitable for ferroptosis and lipid peroxidation research
Rat GPX3 detection	EJ1512347	Rat Glutathione Peroxidase 3 (GPX3) ELISA Kit	BioReagent	Used for GPX3 detection in rat serum, tissue, or model samples
Rat GPX1 detection	EJ1512348	Rat Glutathione Peroxidase 1 (GPX1) ELISA Kit	BioReagent	Used for GPX1 quantification in rat oxidative stress models
Rat GPX4 detection	EJ1512349	Rat Glutathione Peroxidase 4 (GPX4) ELISA Kit	BioReagent	Used for GPX4 detection in rat ferroptosis, myocardial, liver, and kidney injury models
Mouse GPX3 detection	EJ1515180	Mouse Glutathione Peroxidase 3 (GPX3) ELISA Kit	BioReagent	Used for mouse secreted GPX3 and body fluid antioxidant research
Mouse GPX1 detection	EJ1513263	Mouse Glutathione Peroxidase 1 (GPX1) ELISA Kit	BioReagent	Used for GPX1 detection in mouse tissue and cell samples
Mouse GPX4 detection	EJ1513264	Mouse Glutathione Peroxidase 4 (GPX4) ELISA Kit	BioReagent	Used for GPX4 detection in mouse lipid peroxidation and ferroptosis models
Total GSH-Px activity	G1505763	Glutathione Peroxidase (GSH-Px) Activity Assay Kit (DTNB, Micro Method)	BioReagent	Used for total GSH-Px activity detection in cell, tissue, and serum samples
Total GSH-Px activity	G1505754	Glutathione Peroxidase (GSH-Px) Activity Assay Kit (DTNB, Colorimetric Method)	BioReagent	Used for routine spectrophotometric detection of GSH-Px activity
TXNRD1 protein/standard	rp329429	Recombinant Human TXNRD1/TRXR1 Protein	≥95% (SDS-PAGE)	Used for TXNRD1 assay establishment, antibody validation, and positive control
TXNRD1 protein validation	Ab133101	Recombinant TXNRD1 Antibody	ExactAb™, validated, recombinant, 0.7 mg/mL	Used for detecting cytosolic thioredoxin system TXNRD1 expression
TXNRD2 protein validation	Ab133111	Recombinant TXNRD2 Antibody	ExactAb™, validated, recombinant, 0.79 mg/mL	Used for detecting mitochondrial TXNRD2 expression; suitable for mitochondrial oxidative stress research
TXNRD1 expression intervention	T1487291	TXNRD1 Human Pre-designed siRNA Set A		Used for TXNRD1 knockdown and thioredoxin system functional validation
TXNRD2 expression intervention	T1470515	TXNRD2 Human Pre-designed siRNA Set A		Used for TXNRD2 knockdown and mitochondrial antioxidant network research
TXNRD1 negative control sample	P751454	pLenti-TXNRD1-sgRNA		Used for TXNRD1 antibody validation and protein detection negative control
TXNRD1 transcriptional control sample	P751455	pLenti-TXNRD1-sgRNA		Used for TXNRD1 transcription detection and qPCR negative control
TXNRD/TrxR ELISA detection	EJ1512951	Mouse Thioredoxin Reductase (TrxR) ELISA Kit	BioReagent	Used for detecting TrxR/TXNRD levels in mouse samples
TXNRD activity detection	S1507969	Thioredoxin Reductase (TrxR) Activity Assay Kit (DTNB, Micro Method)	BioReagent	Used for total TXNRD activity detection in cells or tissues
TXNRD activity detection	T1515944	Thioredoxin Reductase (TrxR) Activity Assay Kit (DTNB, Colorimetric Method)	BioReagent	Used for colorimetric detection of TrxR/TXNRD activity
TXNRD positive control	T321699	Thioredoxin Reductase from rat liver	EnzymoPure™, buffered aqueous glycerol solution, ≥100 units/mg protein (Bradford)	Used as a positive control for TrxR activity systems and inhibitor screening
Selenium transport intervention	S1466471	SELENOP Human Pre-designed siRNA Set A		Used for SELENOP knockdown to study the relationship between selenium transport and selenoprotein expression
ER stress-related selenoprotein intervention	S1476233	SELENOS Human Pre-designed siRNA Set A		Used for SELENOS knockdown to study ER stress, inflammation, and selenoprotein regulation
Immune/calcium homeostasis selenoprotein intervention	S1475123	SELENOK Human Pre-designed siRNA Set A		Used for SELENOK knockdown to study immune cell function and calcium homeostasis-related selenoprotein effects

9 Common Questions

9.1 Are selenoproteins and antioxidant enzymes the same concept?

No. Some antioxidant enzymes are selenoproteins, such as GPX and TXNRD, but SOD, CAT, PRDX, GSR, and other antioxidant enzymes are not typical selenoproteins. Selenoprotein research should distinguish selenium-dependent antioxidant enzymes from non-selenium-dependent antioxidant enzymes.

9.2 Can GPX activity alone explain selenoprotein function?

Not completely. GPX activity reflects part of selenium-dependent antioxidant function, but it cannot represent TXNRD, SELENOP, SELENOS, or GPX4-specific functions. If the selenoprotein network is being studied, TXNRD, SELENOP, GSH/GSSG, and oxidative injury markers should be added.

9.3 Why is GPX4 commonly used in ferroptosis research?

GPX4 can reduce membrane lipid hydroperoxides and is an important selenoprotein that suppresses lipid peroxidation accumulation. GPX4 reduction or inactivation increases lipid ROS accumulation and promotes ferroptosis-related injury. Interpretation should include lipid ROS, GSH, SLC7A11, and iron metabolism markers.

9.4 Can SELENOP represent selenium nutritional status in the body?

SELENOP is an important selenium transport protein and can reflect selenium supply and liver-derived selenoprotein synthesis status, but it cannot alone represent the selenium status of all tissues. Inflammation, liver function, and nutritional status can all affect SELENOP levels.

9.5 Why does increased antioxidant enzyme activity not necessarily mean enhanced protection?

Increased antioxidant enzymes may represent enhanced defense, but may also be a compensatory response induced by oxidative stress. If ROS, MDA, 4-HNE, or cell injury markers remain elevated, the antioxidant system may still be insufficient to offset oxidative pressure.

9.6 Which selenium compound is more suitable for cell experiments?

Sodium selenite, selenomethionine, methylselenocysteine, and nano-selenium have different metabolic routes. If selenoprotein synthesis is being studied, it is necessary to consider whether the compound can effectively enter the selenocysteine synthesis and selenoprotein translation pathway. If toxicity or antitumor effects are being studied, cell viability and oxidative stress should be monitored simultaneously.

9.7 Is total selenium detection necessary in selenoprotein research?

It is recommended. Total selenium can indicate selenium exposure or selenium storage, but it cannot replace selenoprotein functional detection. An ideal design combines total selenium, SELENOP, GPX/TXNRD activity, and oxidative injury readouts.

Selenoprotein and antioxidant enzyme research should be developed across four levels: selenium supply, selenoprotein expression, enzyme activity function, and oxidative injury outcomes. GPX and TXNRD are the core functional axes. SELENOP reflects selenium transport and supply background, while SOD, CAT, PRDX, GSH/GSSG, and lipid peroxidation markers are used to build a complete redox interpretation system.

For more related articles, please see below:

[1] The Drug Target Potential of the GPX Family in Lipid Peroxidation Defense, Ferroptosis Regulation, and Organ Injury Protection

[2] Combined Detection Strategy for SOD, CAT, and GSH-Px in the Antioxidant Enzyme Defense System