Glycosyltransferases of the human cervical epithelium. I. Characterization of a beta-galactoside alpha-2-L-fucosyltransferase and the identification of a beta-N-acetylglucosaminide alpha-3-L-fucosyltransferase.

ABSTRACT

Using phenyl beta-D-galactoside as an acceptor, alpha-2-L-fucosyltransferase activity was identified in human cervical epithelium with pH optima at 6.0 and 7.2. The different response to p-chloromercuribenzoate, and ability to utilise asialofetuin as an acceptor, suggests the presence of two fucosyltransferases. The acid form is probably involved in glycoprotein synthesis in vivo. At pH 6.0, fucosyltransferase has a temperature optimum of 25 degrees C, requires the presence of Triton X-100 and either manganese or magnesium for maximal activity, and has Km values for GDP-L-[14-C]fucose and phenyl beta-D-galactoside of 32.1 . 10(-6) M and 8.2 . 10(-3) M, respectively. Guanosine nucleotides are potent inhibitors of the fucosyltransferase reaction; GDP is a competitive inhibitor while, depending on its concentration, GTP can either inhibit or activate the reaction. The alpha-L-fucosidase present in cervical tissue has negligible activity towards the enzyme product, phenyl-alpha-2-L-[14C]fucosyl-beta-D-galactoside. The use of high and low molecular weight acceptors indicates the presence of a beta-N-acetylglucosaminide alpha-3-L-fucosyltransferase and an N-acetylgalactosaminide fucosyltransferase.