xylosyltransferase 1 (XylT-1, peptide O-xylosyltransferase 1, XYLT1, XT1)

Function

• catalyzes 1st step in biosynthesis of glycosaminoglycan
• transfers D-xylose from UDP-D-xylose to Ser of nascent glycoprotein
• initial enzyme in biosynthesis of chondroitin sulfate & dermatan sulfate proteoglycans in fibroblasts & chondrocytes
• transfers a beta-D-xylosyl residue from UDP-D-xylose to Ser hydroxy group of an acceptor glycoprotein

Cofactor: divalent cations

Kinetic parameters:

• KM=0.9 uM for recombinant bikunin
• Vmax=764 pmol/h/mg enzyme with recombinant bikunin as substrate

Structure

• monomer, contains 7 disulfide bonds, N-glycosylated
• belongs to the glycosyltransferase 14 family, XylT subfamily

Compartment

• endoplasmic reticulum, Golgi, extracellular together with chondroitin sulfate proteoglycans

Expression

• widely expressed
• expressed in placenta, kidney, pancreas > skeletal muscle

Pathology

• activity is diminished in seminal plasma of unfertile men

More general terms

• glycosyltransferase
• glycoprotein

Database

• OMIM: https://mirror.omim.org/entry/608124
• UniProt: http://www.uniprot.org/uniprot/Q86Y38.html