Classical PTMs

Protein phosphorylation is one of the most abundant and extensively studied post-translational modifications (PTMs). It is a dynamic and reversible process in which protein kinases transfer phosphate groups from ATP to specific amino acid residues, mainly serine (Ser), threonine (Thr), and tyrosine (Tyr). Phosphorylation regulates protein activity, stability, and interactions, and plays essential roles in signal transduction, cell proliferation, cell cycle regulation, and immune response. Dysregulated phosphorylation is closely associated with various human diseases, especially cancer, and serves as an important mechanism for disease research and therapeutic target discovery.

Protein acetylation is a common post-translational modification (PTM) characterized by the addition of acetyl groups to lysine residues or protein N-termini. Regulated by acetyltransferases and deacetylases, acetylation plays important roles in chromatin remodeling, gene expression, protein function regulation, and cellular metabolism. Dysregulated acetylation is associated with various diseases, making acetylation analysis valuable for understanding disease mechanisms and identifying potential therapeutic targets.

Protein methylation refers to the covalent modification of lysine and arginine residues by the addition of methyl groups derived from S-adenosylmethionine (SAM). Lysine methylation, including mono-, di-, and trimethylation (Kme1, Kme2, and Kme3), serves as a key epigenetic mechanism controlling chromatin organization and gene expression. Analysis of protein methylation provides insights into epigenetic regulation and the molecular mechanisms underlying cellular identify and function.

Ubiquitination is a dynamic protein modification that determines the fate and function of target proteins through the covalent attachment of ubiquitin molecules. This process is orchestrated by a sequential enzymatic cascade involving ubiquitin-activating enzymes (E1), ubiquitin-conjugating enzymes (E2), and ubiquitin ligases (E3). Beyond its classical role in proteasome-mediated protein degradation, ubiquitination regulates diverse cellular processes, including protein degradation, trafficking, DNA damage repair, cell cycle progression, and immune responses. Dysregulated ubiquitination is implicated in multiple diseases, particularly cancer and neurodegenerative disorders, making it an important target for disease mechanism studies and therapeutic development.

SUMOylation is a reversible post-translational modification that regulates protein function through the covalent attachment of small ubiquitin-like modifier (SUMO) proteins to specific lysine residues in proteins. This process is mediated by SUMO-related enzymes and regulates diverse cellular process, including protein stability, nuclear transport, transcription, DNA repair, and stress response. Emerging studies have revealed the critical role of SUMOylation in maintaining cellular homeostasis and regulating complex biological processes, making it an important target for understanding protein regulation and cellular function.

Protein glycosylation is an enzymatically regulated process in which glycans are attached to specific amino acid residues of proteins, predominantly occurring in the endoplasmic reticulum (ER) and Golgi apparatus. Major forms of protein glycosylation include N-linked glycosylation and O-linked glycosylation, which differ in their attachment sites and biological functions. Glycosylation plays essential roles in regulating protein folding, stability, trafficking, and function, as well as diverse biological processes such as cell adhesion, cell communication, and immune response. Aberrant glycosylation patterns are closely associated with various pathological conditions, including cancer, inflammation, and autoimmune disorders.