Miscellaneous protein kinases

A protein kinase is an enzyme that selectively modifies other proteins by covalently adding phosphates to them (phosphorylation) as opposed to kinases which modify lipids, carbohydrates, or other molecules. The human genome contains about 500 protein kinase genes and they constitute about 2% of all human genes 1. There are two main types of protein kinase. The great majority are serine/threonine kinases, which phosphorylate the hydroxyl groups of serines and threonines in their targets.