Final answer:
Phosphorylation occurs when a phosphate group bonds with an enzyme, leading to a conformational change that can activate or deactivate the enzyme's function. This process is mediated by kinases and can be reversed by phosphatases, making it a crucial regulatory mechanism in cellular processes.
Step-by-step explanation:
When a phosphate group forms a covalent bond with an enzyme that is covalently modulated, a process called phosphorylation occurs. Phosphorylation refers to the addition of the phosphate to an enzyme, often resulting in a conformational change of the enzyme molecule, which can activate or deactivate its catalytic activity. This modification is typically mediated by an enzyme known as a kinase and utilizes ATP as the phosphate donor. The transfer of the phosphate group involves the formation of a high-energy bond and is often associated with a significant change in the enzyme's properties, such as its shape or charge distribution, which can alter enzyme function or interaction with other molecules.
Such a modification is part of the regulatory mechanism that cells use to control enzyme activity quickly in response to changes in the cell's environment or signals. This is a reversible process, which means the enzyme can return to its original state through the action of another enzyme called a phosphatase, which removes the phosphate group. Therefore, the phosphorylation and dephosphorylation of enzymes serve as on-and-off switches in many cellular processes.