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phosphorylation The introduction of a phosphate group into a biomolecule in a reaction that is normally controlled by a phosphorylase enzyme. Phosphate is able to combine easily with inert organic compounds, making them chemically active. The first stage in many biochemical reactions is phosphorylation. The conversion of AMP and ADP to ATP occurs by phosphorylation reactions in two main metabolic pathways, oxidative phosphorylation and photophosphorylation. The formation of nucleotides also involves a phosphorylation reaction. The activity of many enzymes is controlled by phosphorylation: certain enzymes are activated when they are phosphorylated (see kinase), while others are deactivated. Phosphorylation of these enzymes is under the control of hormones and other messengers.
phosphorylation The addition of a phosphate group to a compound, involving the formation of an ester bond between the reactants.