Activated human enzymes
Molecular enzymology - Enzymatic catalysis

Magnesium ions Mg²⁺ are essential for the activity of kinases catalyzing phosphate group transfer. These enzymes are known as phosphotransferases. Under normal conditions, the Mg²⁺ cation binds to ATP, and the kinases interact with the ATP coenzyme in the form ATP-Mg²⁺. This is an indirect activation.

Calcium cations Ca²⁺ are activators of certain peptidases (peptide catabolism).

The chloride anions Cl^– are activators of certain amylases (starch hydrolysis).