EC 2.7 Transferring phosphorus-containing groups

This subclass contains a rather large group of enzymes that transfer not only phosphate but also diphosphate, nucleotidyl residues and other groups. The phosphotransferases are subdivided according to the acceptor group, which may be an alcohol group (EC 2.7.1), a carboxy group (EC 2.7.2), a nitrogenous group, such as that of creatine (EC 2.7.3), or a phosphate group, as in the case of adenylate kinase (EC 2.7.4). Other sub-subclasses are for: diphosphotransferases (EC 2.7.6), nucleotidyltransferases (EC 2.7.7) and transferases for other substituted phosphate groups (EC 2.7.8). With the enzymes of sub-subclass EC 2.7.9, two phosphate groups are transferred from a donor such as ATP to two different acceptors. The protein kinases are divided into the sub-subclasses protein-tyrosine kinases (EC 2.7.10), protein-serine/threonine kinases (EC 2.7.11), dual-specificity kinases (EC 2.7.12), protein-histidine kinases (EC 2.7.13) and other protein kinases (EC 2.7.99). Where appropriate specific amino acids in peptide substrates that contribute to protein kinase specificity are denoted by their positions relative to the phosphoryl acceptor by the system P-1 to P-n towards the N-terminus and P+1 to P+n towards the C-terminus. This numbering system is commonly used for protein kinases to that used for the peptidases and may be compared to the alternative system used for peptidases, where P1 to Pn and P’1—P’n are used.