More About Transferases
A transferase is an enzyme that catalyzes the transfer of a functional group from one molecule to another. As such, protein kinases are a significant member of this family of enzymes, being capable of transferring phosphorus-containing groups (phosphate) from a donor (usually adenosine triphosphate (ATP)) to specific amino acid residues with a free hydroxyl group of an acceptor in a covalent way[1]. As within the class of oxidoreductases, the class of transferases is divided into subclasses, based on the functional groups the enzymes transfer and the substrate specificity.
[1] The Cell: A Molecular Approach. 2nd edition. Cooper GM. Sunderland (MA): Sinauer Associates; 2000.