External yeast beta-fructosidase. Affinity labeling of the active site.
Conduritol-B-epoxide, a compound structurally related to the substrates of external yeast beta-fructosidase (beta-D-fructofuranoside fructohydrolase, EC 3.2.1.26), is an active-site directed inhibitor of this enzyme. The inactivation is irreversible and first-order with respect to time and inhibitor concentration. From the kinetic data obtained, it is concluded that one molecule of inhibitor reacts with one molecule of the enzyme causing inactivation. The inactivation is prevented by the presence of substrates. The pH-dependence of inactivation shows two dissociating groups in the enzyme with pKa values 3.05 and 6.8 being involved in the inactivation process. A carboxylate at the active site with pKa 3.05 is suggested to be the reactive group with conduritol-B-epoxide.
D000345:Affinity Labels; D001665:Binding Sites; D004852:Epoxy Compounds / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D007294:Inositol / Q000031:analogs & derivatives / Q000494:pharmacology; D007700:Kinetics; D011485:Protein Binding; D012441:Saccharomyces cerevisiae / Q000201:enzymology; D013329:Structure-Activity Relationship; D013393:Sucrase / Q000378:metabolism
D000345:Affinity Labels; D004852:Epoxy Compounds; D007294:Inositol; D013393:Sucrase