PTMS

Post-translational modifications (PTMs) are covalent modifications that occur on proteins after translation. They generate functional diversity by altering chemical properties, structure, stability, localization, interactions, and activity. PTMs are catalyzed by enzymes or occur spontaneously under specific cellular conditions. Common PTMs include phosphorylation of serine, threonine, and tyrosine; ubiquitination and sumoylation on lysine residues; acetylation and methylation of lysine or arginine; glycosylation (N- and O-linked); lipidation such as palmitoylation and prenylation; nitrosylation; ADP-ribosylation; and proteolytic processing. PTMs can be reversible or lead to degradation, and they respond to signaling cues, metabolic state, stress, and developmental signals.

PTMs regulate signaling pathways, transcriptional programs, enzyme activity, protein stability, subcellular localization, and protein–protein interactions. Dysregulation of PTMs is associated with diseases including cancer, neurodegenerative disorders, metabolic syndromes, and immune dysfunction.

Detection and study rely on mass spectrometry for site-specific mapping, antibody-based assays for specific marks, and enrichment techniques to enhance detection of low-abundance modifications. Bioinformatic databases curate PTM sites and functions (such as UniProt and dbPTM). PTMs present analytical challenges due to sub-stoichiometry, dynamic turnover, and labile chemistry. In systems biology, PTM networks help illustrate how signaling states govern cellular outcomes and how information flows across pathways. The study of PTMs continues to reveal additional layers of regulation that expand the functional proteome beyond the gene-encoded sequence.