title: alpha-D-Mannosidase of Saccharomyces cerevisiae. Characterization and modulation of activity.
abstract: A unique and interesting alpha-D-mannosidase (alpha-D-mannoside mannohydrolase EC 3.2.1.24) activity has been isolated from Saccharomyces cerevisiae. The enzyme was localized in a crude particulate fraction of the cell extract and was not solubilized by treatment with detergents or high ionic strength NaCl. The enzyme had a pH optimum of 6.3, Km 50 micron with p-nitrophenyl-alpha-D-mannopyranoside, and was competitively inhibited by D-mannose (Ki 20 mM). The enzyme is not affected by ethylenediaminetetraacetic acid, a number of different cations, or sulfhydryl reagents. It was inhibited by p-chloromercuriphenyl sulfonic acid and this inhibition is prevented by the addition of substrate. The cellular concentration of alpha-D-mannosidase is inversely proportional to growth rate, suggesting that the enzyme is under catabolite repression. The level of enzyme was found to increase approx. 8-fold during sporulation. This is apparently due to de novo synthesis, since inhibition of protein synthesis by cycloheximide prevents the increase in enzyme activity.
mesh_terms: D003513:Cycloheximide / Q000494:pharmacology; D007700:Kinetics; D008361:Mannosidases / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000201:enzymology*; D013172:Spores, Fungal / Q000201:enzymology
chemical_list: D003513:Cycloheximide; D008361:Mannosidases