title: [Study of the topology of the active center of glycosidases of Aspergillus niger].
abstract: Activity of alpha-N-acetylgalactosaminidase and alpha-galactosidase isolated from the culture medium of micromycete Aspergillus niger v. Tiegh F-16694 has been studied as affected by anions, cations and specific chemical reagents (n-chlormercurybenzoate, L-cysteine, dithiotreitol, beta-mercaptoethanol, EDTA, o-phenanthroline, sodium azide, hydrogen peroxide). It has been established that silver ions noncompetitively inhibit alpha-galactosidase at pH 5.2, the inhibition constant (Ki) being 2.5 x 10(-4) M. Galactose in concentration of 1-5 mM does not protect the enzyme from the negative action of silver ions, but this inhibitory effect is almost completely removed by the corresponding concentrations of L-cysteine. The same noncompetitive character was inherent in the inhibition of alpha-galactosidase reaction by mercury ions and n-chlormercurybenzoat (Ki is 4.5 x 10(-6) and 1.8 x 10(-4), respectively). The importance of sulphydryl groups for the support of active comformation of alpha-galactosidase molecule was established on the basis of inhibition and kinetic analysis. It has been shown that the enzyme molecule does not contain the groups which include metal atoms.
authors.forename: N V
authors.initials: NV
authors.lastname: Borzova
authors.forename: L D
authors.initials: LD
authors.lastname: Varbanets'
mesh_terms: D001234:Aspergillus niger / Q000201:enzymology*; D001665:Binding Sites; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D000519:alpha-Galactosidase / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*
chemical_list: D004791:Enzyme Inhibitors; D000519:alpha-Galactosidase