Galactosylxylosylprotein 3-beta-galactosyltransferase

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In enzymology, a galactosylxylosylprotein 3-beta-galactosyltransferase (EC 2.4.1.134) is an enzyme that catalyzes the chemical reaction

UDP-galactose + 4-beta-D-galactosyl-O-beta-D-xylosylprotein $\rightleftharpoons$ UDP + 3-beta-D-galactosyl-4-beta-D-galactosyl-O-beta-D-xylosylprotein

Thus, the two substrates of this enzyme are UDP-galactose and 4-beta-D-galactosyl-O-beta-D-xylosylprotein, whereas its two products are UDP and 3-beta-D-galactosyl-4-beta-D-galactosyl-O-beta-D-xylosylprotein.

This enzyme belongs to the family of glycosyltransferases, specifically the hexosyltransferases. The systematic name of this enzyme class is UDP-galactose:4-beta-D-galactosyl-O-beta-D-xylosylprotein 3-beta-D-galactosyltransferase. Other names in common use include galactosyltransferase II, and uridine diphosphogalactose-galactosylxylose galactosyltransferase. This enzyme participates in chondroitin sulfate biosynthesis and glycan structures - biosynthesis 1. It employs one cofactor, manganese.

[edit] References

IUBMB entry for 2.4.1.134
BRENDA references for 2.4.1.134 (Recommended.)
PubMed references for 2.4.1.134
PubMed Central references for 2.4.1.134
Google Scholar references for 2.4.1.134
Robinson JA, Robinson HC (1985). "Initiation of chondroitin sulphate synthesis by beta-D-galactosides Substrates for galactosyltransferase II". Biochem. J. 227: 805–14. PMID 3924029.
Schwartz NB, Roden L (1975). "Biosynthesis of chondroitin sulfate. Solubilization of chondroitin sulfate glycosyltransferases and partial purification of uridine diphosphate-D-galactose:D-xylose galactosyltrans". J. Biol. Chem. 250: 5200–7. PMID 1150655.
Bai X, Zhou D, Brown JR, Crawford BE, Hennet T, Esko JD (2001). "Biosynthesis of the linkage region of glycosaminoglycans: cloning and activity of galactosyltransferase II, the sixth member of the beta 1,3-galactosyltransferase family (beta 3GalT6)". J. Biol. Chem. 276: 48189–95. PMID 11551958.