kinase

(kī'nās', -nāz', kĭn'ās', -āz')
n.
Any of various enzymes that catalyze the transfer of a phosphate group from a donor, such as ADP or ATP, to an acceptor.

[KIN(ETIC) + -ASE.]

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An enzyme that catalyses the transfer of a phosphate group from ATP to an acceptor (see phosphofructokinase).

any phosphotransferase enzyme that transfers a phosphate group, usually from ATP. Kinases are divided into EC sub-subclasses according to the nature of the phosphate-accepting group: EC 2.7.1 — phosphotransferases with an alcohol group as acceptor; EC 2.7.2 — phosphotransferases with a carboxyl 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. The name is also used for enzymes that transfer a phosphate group from other nucleoside triphosphates. Compare dikinase, pyrophosphokinase, thiokinase.

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1. a subclass of the transferases, comprising the enzymes that catalyze the transfer of a high-energy group from a donor (usually ATP) to an acceptor, and named, according to the acceptor, as creatine kinase, fructokinase, etc.
2. an enzyme that activates a zymogen, and named, according to its source, as enterokinase, streptokinase, etc.

• protein k's — cellular enzymes which utilize ATP to phosphorylate proteins, usually at a selected OH group of serine, threonine or tyrosine residue in the protein, so as to increase or decrease the activity of the protein.
• protein k. C — membrane bound protein kinase designated C because it requires Ca²+ and phosphatidyl serine for its activity. Activated by sn-1,2-diacylglycerol (DAG) produced from phosphatidyl inositol 4,5-bisphosphate. Phosphorylates target proteins such as the insulin receptor, β-adrenergic receptor, glucose transporter, HMG-CoA reductase, cytochrome P-450 and tyrosine hydroxylase.

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