Substrate specificity and kinetic properties of alpha-galactosidases from Vicia faba.
1. The hydrolysis of a variety of galactosides and other glycosides by alpha-galactosidases I and II of Vicia faba was studied. 2. The effect of temperature on kinetic parameters was also examined. 3. Both enzymes are inhibited by excess of substrate (p-nitrophenyl alpha-d-galactoside); with enzyme I this is competitive and is caused by the galactosyl moiety. 4. Enzyme I is inhibited by oligosaccharides possessing terminal non-reducing galactose residues and to a smaller extent by l-arabinose and d-fucose. 5. The effect of pH on K(m) and V(max.) values suggests that carboxyl and imidazole groups are involved in the catalytic activity of enzyme I. 6. Photo-oxidation experiments with enzyme I also suggest that an imidazole group is present at the active site.
D001089:Arabinose / Q000494:pharmacology; D005643:Fucose / Q000494:pharmacology; D005696:Galactosidases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D006027:Glycosides / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007093:Imidazoles; D007700:Kinetics; D009844:Oligosaccharides / Q000494:pharmacology; D012639:Seeds / Q000201:enzymology*; D013696:Temperature
D006027:Glycosides; D007093:Imidazoles; D009844:Oligosaccharides; D005643:Fucose; D001089:Arabinose; D005696:Galactosidases