Kinase

Kinases are enzymes that transfer a phosphate group from adenosine triphosphate (ATP) , or other trinucleotide, to a number of biological substrates, such as sugars or proteins. They are part of a larger family of enzymes known as group transferases, but are limited to phosphate transfers. A typical reaction catalyzed by a kinase (e.g., hexokinase) is the phosphorylation of glucose upon its entry into a cell

Glucose + ATP → Glucose-6-phosphate + ADP

This reaction sets the stage for the subsequent metabolism of glucose via a number of metabolic pathways. Creatine kinase (CK), which transfers a phosphate from ATP to creatine, acts to store some of the energy of ATP in the muscle molecule creatine. CK levels in blood are measured in blood tests to diagnose heart attacks, as damaged heart muscle cells release CK into the bloodstream. Recently there has been great interest in the phosphorylation of specific amino acids in proteins. This modification acts as a regulation of the protein's activity. Hormonal signals outside a cell initiate a cascade of biochemical events inside the cell that include activation of a number of protein kinases. Of further interest in kinase regulation is the fact that several cancer-causing genes (oncogenes) code for kinases. The lack of regulation of these genes may be important in the etiology of cancer.

see also Amino Acid; Enzymes.

C. Larry Bering

Bibliography

Moran, Laurence E.; Scrimgeour, K. Gray; Horton, H. Robert; et al. (1994). Biochemistry, 2nd edition. Englewood Cliffs, NJ: Prentice Hall.

Internet Resources

"The Protein Kinase Resource Center." San Diego Supercomputer Center. Available from <http://www.sdsc.edu>.

kinase (phosphokinase) An enzyme that can transfer a phosphate group from a high-energy phosphate, such as ATP, to an organic molecule. Phosphorylation is normally required to activate the molecule, which is often an enzyme. For example, kinases activate the precursors of enzymes secreted in pancreatic juice (see chymotrypsin; trypsin). See also protein kinase.

kinase An enzyme that catalyses reactions involving the transfer of phosphates from a nucleoside triphosphate, particularly ATP, to another substrate.

kinase An enzyme that catalyses reactions involving the transfer of phosphates from a nucleoside triphosphate, particularly ATP, to another substrate.

kinase (ky-nayz) n.
1. an agent that can convert the inactive form of an enzyme (see proenzyme) to the active form.

2. an enzyme that catalyses the transfer of phosphate groups.