Presence of UDP-D-xylose: beta-D-glucoside alpha-1,3-D-xylosyltransferase involved in the biosynthesis of the Xyl alpha 1-3Glc beta-Ser structure of glycoproteins in the human hepatoma cell line HepG2.
HepG2 cells were examined for the presence of UDP-D-xylose: beta-D-glucoside alpha-1,3-xylosyltransferase activity by using 2-[(2-pyridyl)amino]ethyl beta-D-glucopyranoside (Glc beta-R) as a fluorogenic acceptor. UDP-D-xylose and the acceptor were incubated with the HepG2 microsomal fraction, and the enzymatic reaction mixture was analyzed by HPLC. Structural analysis of the fluorogenic product by alpha-D-xylosidase digestion, FAB-MS, and Smith degradation revealed that it was Xyl alpha 1-3Glc beta-R, thus demonstrating the existence of beta-D-glucoside alpha-1,3-xylosyltransferase. A solubilization study of the enzyme from the microsomal fraction indicated that it differed from UDP-D-xylose: alpha-D-xylodie alpha-1,3-xylosyltransferase of the HepG2 microsomal fraction producing Xyl alpha 1-3Xyl alpha 1-3Glc-R' [R', (2-pyridyl)amino-] from UDP-D-xylose and Xyl alpha 1-3Glc-R' [Minamida, S., Aoki, K., Natsuka, S., Omichi, K., Fukase, K., Kusumoto, S. & Hase, S. (1996) J. Biochem. (Tokyo) 120, 1002-1006]. The newly detected enzyme appears to be involved in the biosynthesis of the Xyl alpha 1-3Glc beta-Ser structure of glycoproteins such as human blood coagulation factors VII and IX.
Omichi
K
K
Department of Chemistry, Graduate School of Science, Osaka University, Japan.
Aoki
K
K
Minamida
S
S
Hase
S
S
D006528:Carcinoma, Hepatocellular / Q000201:enzymology*; D002851:Chromatography, High Pressure Liquid; D005947:Glucose; D006023:Glycoproteins / Q000096:biosynthesis*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008113:Liver Neoplasms / Q000201:enzymology*; D008861:Microsomes / Q000201:enzymology; D010430:Pentosyltransferases / Q000302:isolation & purification* / Q000378:metabolism; D012694:Serine; D012995:Solubility; D016339:Spectrometry, Mass, Fast Atom Bombardment; D014407:Tumor Cells, Cultured; D014994:Xylose
D006023:Glycoproteins; D012694:Serine; D014994:Xylose; D010430:Pentosyltransferases; C105769:UDP-D-xylose-beta-D-glucoside alpha-1,3-xylosyltransferase; C105770:UDP-D-xylose-xyloside alpha-1,3-xylosyltransferase; D005947:Glucose