Enzymatic characterization of UDP-galactose:FdSdG galactosyltransferase in purified liver plasma membrane
Fernandez-Briera, A.; Louisot, P.; Morelis, R.
Biochemistry International 18(2): 415-428
1989
ISSN/ISBN: 0158-5231 PMID: 2504163 Document Number: 330817
This study yields evidence for the localization of a galactosyltransferase in purified liver plasma membranes, with the following results. The purified plasma membranes contained galactosyltransferases which transfered galactose from UDP-galactose into desialylated-degalactosylated fetuine. A suitable system of glycosylation reaction was defined. It contained: 10 mM Tris-HCl pH 7.4, 5 mM Mn2+, 4 mM NaF. For the assay with exogenous acceptors, 1.6 mg/ml of desialylated-degalactosylated fetuine and 0.1% of triton X-100 were added. The apparent Km values for UDP-galactose were about 10(-5) M. Enzymatic activities required Mn2+. This cation appeared to be a linear non-competitive activator when used at concentrations below 5 mM. Mg2+ and Ca2+ had an inhibitory effect on Mn2+-dependant-galactosyltransferase.