Peptide O-xylosyltransferase (XT)

Peptide O-xylosyltransferase (XT) is a critical enzyme family, consisting of isoforms XYLT1 and XYLT2, that catalyzes the initial and rate-limiting step in the biosynthesis of glycosaminoglycan (GAG) chains on proteoglycans. It functions by transferring xylose from UDP-xylose to specific serine residues within the core proteins of proteoglycans as they pass through the endoplasmic reticulum and Golgi apparatus (UniProt Q86Y01, Q9H1B5). This modification is essential for the subsequent elongation of chondroitin sulfate, dermatan sulfate, and heparan sulfate chains, which are vital components of the extracellular matrix (ECM) and cell surface (PubMed: 22614068). In pathological conditions, elevated XT activity is strongly associated with fibroproliferative diseases, such as systemic sclerosis and liver fibrosis, where excessive GAG production leads to tissue scarring. Conversely, genetic mutations in XYLT genes are linked to severe skeletal disorders, including Desbuquois dysplasia, characterized by short stature and joint laxity (PubMed: 23681206). Because of its central role in ECM remodeling, XT has emerged as a therapeutic target for anti-fibrotic drug development. Current research focuses on small molecule inhibitors and decoy xylosides to modulate XT activity, though no XT-specific drugs are currently FDA-approved for clinical use (PubMed: 24705139).

Other names

XylosyltransferaseUDP-D-xylose:proteoglycan core protein beta-D-xylosyltransferaseXYLT1XYLT2Protein xylosyltransferase

Inhibition of enzyme activity to reduce the synthesis of glycosaminoglycan chains on proteoglycans, or use of xyloside derivatives as decoy substrates to prevent proper extracellular matrix assembly.