Ester bond enzymes are a class of enzymes that catalyze the formation or hydrolysis of ester bonds. Ester bonds are a type of covalent bond that is formed between a carboxylic acid and an alcohol, resulting in the formation of an ester molecule. Ester bond enzymes are involved in a wide range of biological processes, including the biosynthesis and degradation of lipids, carbohydrates, and proteins.