title: N-phenylglucosylamine hydrolysis: a mechanistic probe of β-glucosidase.
abstract: The spontaneous hydrolysis of glycosylamines, where the aglycone is either a primary amine or ammonia, is over a hundred million-times faster than that of O- or S-glycosides. The reason for this (as pointed out by Capon and Connett in 1965) is that, in contrast to the mechanism for O- or S-glycoside hydrolysis, hydrolysis of these N-glycosides (e.g., glc-NHR) involves an endocyclic C-O bond cleavage resulting in formation of an imine (iminium ion) which then reacts with water. Since ring-opening is kinetically favored with glycosylamines, compounds such as phenylglucosylamine can be a useful probes of enzymes that have been suggested to possibly follow this mechanism. With β-glucosidase from sweet almonds, the enzyme is highly efficient in catalyzing the hydrolysis of phenyl glucoside (k(cat)/k(non)∼10(14)) and phenyl thioglucoside (k(cat)/k(non)∼10(10)) while with either the almond or the Aspergillus niger enzyme or with yeast α-glucosidase, there is no detectable catalysis of phenylglucosylamine hydrolysis (k(cat)/k(non)<20). These results are consistent with the generally accepted mechanism involving exocyclic bond cleavage by these enzymes.
authors: Department of Chemistry, Tulane University, New Orleans, LA 70118, USA.
authors: Ying
authors: Y
authors: Na
authors: Hong
authors: H
authors: Shen
authors: Larry D
authors: LD
authors: Byers
mesh_terms: D000814:Aniline Compounds / Q000378:metabolism*; D001234:Aspergillus niger / Q000201:enzymology; D055162:Biocatalysis; D005960:Glucosides / Q000378:metabolism*; D006868:Hydrolysis; D007097:Imines / Q000737:chemistry; D007700:Kinetics; D027861:Prunus / Q000201:enzymology*; D012441:Saccharomyces cerevisiae / Q000201:enzymology; D013863:Thioglucosides / Q000378:metabolism*; D000520:alpha-Glucosidases / Q000378:metabolism; D001617:beta-Glucosidase / Q000378:metabolism*
chemical_list: D000814:Aniline Compounds; D005960:Glucosides; D007097:Imines; D013863:Thioglucosides; C033857:phenylglucoside; D000520:alpha-Glucosidases; D001617:beta-Glucosidase