Kinases

phosphotransferases, a group of enzymes belonging to the transferases that transfer phosphate groups from adenosine triphosphoric acid (ATP) to a variety of substrates (predominantly to the hydroxyl groups of alcohols, carbohydrates, or amino acids).

The presence of magnesium ions (Mg²⁺) is necessary for all kinases (these ions serve as the connecting link between ATP and protein). The kinases include enzymes that make for the utilization of glycogen and glucose in the cell (phosphorylase, hexokinase, phosphofructokinase, pyruvate kinase) and enzymes that participate in the synthesis of coenzymes (NAD-kinase, riboflavin kinase, pyridoxal kinase). They also include the protein kinases, which bring about the phosphorylation of proteins. Kinase reactions entailing the conversion of the energy-rich APT bond to an energy-poor bond are practically irreversible. By contrast, acetate kinase, carbamate kinase, creatine kinase, adenylate kinase (myokinase), nucleoside monophosphate kinase, and nucleoside diphosphate kinase catalyze reactions in which there is a transfer of phosphate groups without a loss of energy; these reactions are readily reversible.

Hydrolytic enzymes (enterokinase, thromobokinase, plasminokinase), although they are also called kinases, do not belong to the above group.