Two α‐3‐ d ‐Galactosyltransferases in Rabbit Stomach Mucosa with Different Acceptor Substrate Specificities

作者：Alan Betteridge, Winifred M. Watkins · 发表于：European Journal of Biochemistry · 年份：1983 · DOI：10.1111/j.1432-1033.1983.tb07321.x · 被引用次数：55 · 研究领域：Amino Acid Enzymes and Metabolism、Digestive system and related health、Diet, Metabolism, and Disease

Homogenates of rabbit stomach mucosa were examined for enzymes catalysing the transfer of D-galactose from UDP-D-galactose to various low-molecular-weight acceptors of known structure. Treatment of the products with alpha and beta-D-galactosidases revealed that D-galactose was transferred in both alpha and beta-anomeric linkages. The beta-D-galactosyltransferase used N-acetylglucosamine and compounds containing terminal nonreducing beta-N-acetylglucosaminyl residues as acceptor substrates. The compounds accepting D-galactose in alpha-anomeric linkage had unsubstituted terminal non-reducing beta-D-galactosyl units or a fucose substituent on the carbon-2 position of a subterminal beta-D-galactosyl unit. Methylation analysis of the products formed with N-acetyllactosamine [beta-D-Galp(1 leads to 4)D-GlcNAcp] and 2'fucosyllactose [alpha-L-Fucp(1 leads to 2)-beta-D-Galp(1 leads to 4)D-Glcp] revealed that D-galactose was transferred to the carbon-3 position of the beta-D-galactosyl residue in both of these acceptor substrates. Competition experiments with the two substrates indicated that the transfer of D-galactose was catalysed in each case by a different alpha-3-D-galactosyltransferase. Differences were also observed in the solubility properties of the enzymes: the alpha-3-D-galactosyltransferase using acceptor substrates with unsubstituted beta-D-galactosyl residues was more readily soluble both in the presence and absence of detergents than the transferase using beta-D-galacto...