Structure-reactivity relationships for beta-galactosidase (Escherichia coli, lac Z). 2. Reactions of the galactosyl-enzyme intermediate with alcohols and azide ion

Biochemistry
J P RichardJ Beard

Abstract

Velocities for the synthesis of beta-D-galactopyranosyl derivatives by transfer of the galactosyl group from beta-galactosidase to seven alkyl alcohols, glucose, and azide ion have been determined as the difference in the velocities for beta-galactosidase-catalyzed cleavage of 4-nitrophenyl beta-D-galactopyranoside to give 4-nitrophenoxide anion (v PNP) and hydrolysis of this compound to give D-galactose (v Gal). Rate constant ratios kROH/ks (M-1) for partitioning of the galactosylated enzyme between reaction with alkyl alcohols and solvent determined by this method are in good agreement with values of kROH/ks (M-1) determined by analysis of alcohol inhibition of enzyme-catalyzed hydrolysis of the corresponding alkyl beta-D-galactopyranosides. Absolute rate constants kROH (M-1 s-1) for reaction of alkyl alcohols with the galactosylated enzyme intermediate were calculated from the corresponding rate constant ratio kROH/ks (M-1) and ks = 710 s-1. A Brønsted parameter of (beta nuc) ROH = -0.19 +/- 0.10 was determined from the second-order rate constants for the reactions of alcohols with the galactosylated enzyme. The large difference between (beta 1g)kcat/Km = -0.75 +/- 0.14 for cleavage of alkyl beta-D-galactopyranosides to form...Continue Reading

Citations

Jan 1, 2013·Applied Biochemistry and Biotechnology·Andrew N W BellDavid J Timson
Jan 30, 2013·Carbohydrate Research·Cecilia Porciúncula GonzálezCecilia Giacomini
Jul 7, 1999·The Biochemical Journal·C Eis, B Nidetzky
Jan 1, 1997·Annual Review of Biochemistry·G J Narlikar, D Herschlag
Mar 16, 2016·Journal of Agricultural and Food Chemistry·Sheryl Lozel ArreolaThu-Ha Nguyen
Mar 17, 2015·Biochimica Et Biophysica Acta·Miaomiao Xie, Larry D Byers
May 4, 2021·Accounts of Chemical Research·John P RichardTina L Amyes
Nov 1, 2005·EcoSal Plus·Christoph Mayer, Winfried Boos
Nov 17, 2015·Journal of the American Chemical Society·Xiang ZhaiJohn P Richard

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