title: A bireactant, irreversible, active-site-directed inhibitor of beta-D-galactosidase (Escherichia coli). Synthesis and properties of (1/2,5,6)-2-(3-azibutylthio)-5,6-epoxy-3-cyclohexen-1-ol.
abstract: (1/2,5,6)-2-(3-Azibutylthio)-5,6-epoxy-3-cyclohexen-1-ol (1) was synthesized and was found to irreversibly inactivate beta-D-galactosidase (Escherichia coli). The inactivation was prevented by the presence of isopropyl 1-thio-beta-D-galactopyranoside (IPTG). The vinyloxirane group of 1 reacted with water and other nucleophiles, especially at higher pH values. Reaction of 1 with beta-D-galactosidase was slow enough so that a competitive-inhibition constant (Ki) of 29mM could be determined. The inhibition constant for (1,2/3,6)-6-(3-azibutylthio)-2-bromo-4-cyclohexene-1,3-diol (2), the precursor of the bireactant inhibitor 1, was 13 mM, while that of (1,3/2,4)-3-(3-azibutylthio)-5-cyclohexene-1,2,4-triol (3), the product formed when the reactant is allowed to react with water, was 23mM. After irradiation by light, beta-D-galactosidase that had initially been treated with the bireactant compound and then digested with trypsin, showed a new pattern of elution from h.p.l.c., indicating that there was reaction at two regions of the beta-D-galactosidase molecule.
authors.affiliation: Division of Biochemistry, Faculty of Science, University of Calgary, Alberta, Canada.
authors.forename: R E
authors.initials: RE
authors.lastname: Huber
authors.forename: J
authors.initials: J
authors.lastname: Lehmann
authors.forename: L
authors.initials: L
authors.lastname: Ziser
mesh_terms: D001391:Azo Compounds / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D001665:Binding Sites; D003511:Cyclohexanols / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D004926:Escherichia coli / Q000201:enzymology; D007544:Isopropyl Thiogalactoside; D007700:Kinetics; D001616:beta-Galactosidase / Q000037:antagonists & inhibitors*
chemical_list: D001391:Azo Compounds; D003511:Cyclohexanols; C071625:2-(3-azibutylthio)-5,6-epoxy-3-cyclohexen-1-ol; D007544:Isopropyl Thiogalactoside; D001616:beta-Galactosidase