phosphorylation phos·pho·ryl·a·tion (fŏs'fər-ə-lā'shən)
The addition of phosphate to an organic compound through the action of a phosphorylase or kinase.
The addition of a phosphate group to an organic molecule. Phosphorylation is important for many processes in living cells. ATP is formed during cell respiration from ADP by phosphorylation, as in the mitochondria of eukaryotic cells (oxidative phosphorylation) and the chloroplasts of plant cells (photosynthetic phosphorylation). Phosphorylation also regulates the activity of proteins, such as enzymes, which are often activated by the addition of a phosphate group and deactivated by its removal (called dephosphorylation).