Phosphotransferases are a category of enzymes (EC number 2.7) that catalyze phosphorylation reactions. The general form of the reactions they catalyze is:
- A-P + B B-P + A
Where P is a phosphate group and A and B are the donating and accepting molecules, respectively.
Phosphotransferases are generally classified according to the acceptor molecule.
- EC 2.7.1 Phosphotransferases with an alcohol group as acceptor
- EC 2.7.2 Phosphotransferases with a carboxy group as acceptor
- EC 2.7.3 Phosphotransferases with a nitrogenous group as acceptor
- EC 2.7.4 Phosphotransferases with a phosphate group as acceptor
- EC 2.7.9 Phosphotransferases with paired acceptors. In these reactions, a single triphosphate-nucleotide transfers two phosphates to two different acceptor molecules, resulting in a monophosphate-nucleotide and two phosphorylated products.
The phosphotransferase system (PTS) is a complex group translocation system present in many bacteria. The PTS transports sugars (such as glucose, mannose, and mannitol) into the cell. The first step of this reaction is phosphorylation of the substrate via phosphotransferase during transport. In the case of glucose, the product of this phosphorylation is glucose-6-phosphate (Glc-6P).Due to the negative charge of the phosphate, this Glc-6P can no longer freely leave the cell. This is the first reaction of glycolysis, which degrades the sugar to pyruvate.
- ^  Phosphotransferases are any enzyme of sub-subclasses EC 2.7.1 to 2.7.4, and EC 2.7.9
- ^ , Classification in this article follows the rules of Enzyme Nomenclature of the Nomenclature Committee of the International Union of Biochemistry and Molecular Biology (NC-IUBMB).