title: Inhibition of yeast exoglucanases by glucosidase inhibitors.
abstract: Castanospermine, 1-deoxynojirimycin, and N-methyl-1-deoxynojirimycin, three well-characterized inhibitors of the glucosidases involved in the processing of N-linked oligosaccharides, did not affect the biosynthesis or the secretion of exoglucanases (EC 3.2.1.58) from Saccharomyces cerevisiae and Candida albicans but inhibited the activity itself. Regardless of the substrate used, laminarin or p-nitrophenyl beta-D-glucoside (pNPG), all three inhibitors proved to act in a competitive manner. Castanospermine was the most potent inhibitor, with Ki values ranging from 0.16 to 0.5 microM for three different purified yeast exoglucanases. The inhibition caused by 1-deoxynojirimycin and N-methyl-1-deoxynojirimycin was poorer, but still significant. By contrast, the glucosidase inhibitors did not show any action on a partially purified endoglucanase (EC 3.2.1.39) Candida albicans. A purified exoglucanase from Basidiomycete QM 806, which was specific for laminarin, was unaffected by castanospermine but it was still inhibited in an uncompetitive manner by 1-deoxynojirimycin and N-methyl-1-deoxynojirimycin. The presence of castanospermine in the culture medium of growing yeasts did not have any effect on yeast growth in spite of the fact that, under the conditions used, the external exoglucanase was fully inhibited. None of the yeast exoglucanases hydrolyzed the glucan synthesized in vitro by membrane preparations derived from either yeast. These results support the concept that yeast exoglucanases are glucosidases that also attack laminarin, rather than glucanases capable of attacking pNPG.
authors.affiliation: Departamento de Microbiología, Facultad de Ciencias, Universidad de Extremadura, Badajoz, Spain.
authors.forename: J C
authors.initials: JC
authors.lastname: Ridruejo
authors.forename: M D
authors.initials: MD
authors.lastname: Muñoz
authors.forename: E
authors.initials: E
authors.lastname: Andaluz
authors.forename: G
authors.initials: G
authors.lastname: Larriba
mesh_terms: D017485:1-Deoxynojirimycin / Q000031:analogs & derivatives; D000470:Alkaloids / Q000494:pharmacology*; D000900:Anti-Bacterial Agents; D001667:Binding, Competitive; D002176:Candida albicans / Q000187:drug effects / Q000201:enzymology*; D043326:Glucan 1,3-beta-Glucosidase; D005936:Glucans; D005944:Glucosamine / Q000031:analogs & derivatives* / Q000494:pharmacology; D005959:Glucosidases / Q000037:antagonists & inhibitors*; D005960:Glucosides / Q000378:metabolism; D007212:Indolizines; D011134:Polysaccharides / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000201:enzymology*; D001617:beta-Glucosidase / Q000037:antagonists & inhibitors* / Q000302:isolation & purification; D054836:Indolizidines
chemical_list: D017485:1-Deoxynojirimycin; D000470:Alkaloids; D000900:Anti-Bacterial Agents; D043326:Glucan 1,3-beta-Glucosidase; D005936:Glucans; D005944:Glucosamine; D005959:Glucosidases; D005960:Glucosides; D007212:Indolizines; D011134:Polysaccharides; D001617:beta-Glucosidase; C025193:4-nitrophenyl beta-D-glucoside; C008247:laminaran; C037806:castanospermine; D054836:Indolizidines; C033424:N-methyldeoxynojirimycin