Post-Translational Modification
A chemical change made to a peptide or protein after it has been synthesised, which can affect the molecule's stability, activity, or interactions. Common modifications include phosphorylation, glycosylation, amidation, and the formation of disulphide bonds.
Technical Context
Common PTMs include: phosphorylation (addition of phosphate groups, key in cell signalling), glycosylation (attachment of sugar chains, affects folding and stability), acetylation (addition of acetyl groups), methylation, hydroxylation (critical for collagen stability — requires vitamin C), amidation (C-terminal modification common in bioactive peptides), and disulphide bond formation. In therapeutic peptide development, PTMs can be deliberately introduced or prevented to optimise drug properties. PEGylation and lipidation are artificial PTMs applied to therapeutic peptides to extend half-life. Understanding which PTMs are present on endogenous peptides helps explain why some synthetic analogues differ from their natural templates.