phosphorylate

Phosphorylate means to introduce a phosphate group into an organic molecule. In biological contexts, phosphorylation most often refers to the transfer of a phosphate group from a donor such as ATP to a substrate, forming a phosphate ester or phosphate monoester and releasing ADP. The reverse process, dephosphorylation, is carried out by phosphatases.

Mechanism: In living systems, phosphorylation is typically catalyzed by kinases. The phosphate donor is usually ATP; the reaction requires Mg2+ and the enzyme active site. The transferred group can attach to hydroxyl, amino, or thiol groups on proteins, sugars, or lipids, yielding phosphoproteins, sugar phosphates, or phospholipids. In non-biological chemistry, phosphorylation can be achieved with reagents such as phosphoryl chlorides or phosphorus oxychloride, and can involve inorganic phosphate (Pi) as a donor in some conditions.

Biological role: Phosphorylation is a key regulatory modification that alters enzyme activity, interactions, localization, and stability. It enables signaling cascades; for example, phosphorylation of serine, threonine, or tyrosine residues controls many cellular processes. Phosphorylation of glucose to glucose-6-phosphate by hexokinase traps glucose in cells and commits it to metabolism. Reversible cycles of phosphorylation and dephosphorylation regulate metabolism, transcription, and cell division.

Other contexts: Phosphorylation of lipids forms phospholipids and signaling lipids such as phosphatidylinositol phosphates, which participate in membrane signaling. In biotechnological synthesis, controlled phosphorylation is used to prepare nucleotide derivatives and various organophosphates.