| Abstrakt: |
HepG2 cells were examined for the presence of UDP-D-xylose:β-D-glucoside α-1,3-xylosyltransferase activity by using 2-[(2-pyridyl)amino]ethyl β-D-glucopyranoside (Glcβ-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 α-D-xylosidase digestion, FAB-MS, and Smith degradation revealed that it was Xylα1-3Glcβ-R, thus demonstrating the existence of β-D-glucoside α-1,3-xylosyltransferase. A solubilization study of the enzyme from the microsomal fraction indicated that it differed from UDP-D-xylose:α-D-xyloside α-l,3-xylosyltransferase of the HepG2 microsomal fraction producing Xylα1-3Xylα1-3Glc-R′ [R′, (2-pyridyl)amino-] from UDP-D-xylose and Xylαl-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 Xylαl-3Glcβ-Ser structure of glycoproteins such as human blood coagulation factors VII and IX. [ABSTRACT FROM AUTHOR] |
