Illustrated Glossary of Organic Chemistry

Kinase: An enzyme that mediates phosphorylation.

In the first step of glycolysis, the hydroxyl group on carbon-6 of glucose is converted from an alcohol to a phosphate ester (i.e., it is phosphorylated). In this phosphorylation reaction the phosphate group is taken from ATP, and the transfer is mediated by hexokinase (a kinase enzyme) and a Mg²⁺ cation.