Oxygen-18 leaving group kinetic isotope effects on the hydrolysis of nitrophenyl glycosides. 1. .beta.-Galactosidase-catalyzed hydrolysis

Biochemistry ◽  
1981 ◽  
Vol 20 (11) ◽  
pp. 3189-3196 ◽  
Author(s):  
Steven Rosenberg ◽  
Jack F. Kirsch
Keyword(s):  
Isotope Effects ◽  
Kinetic Isotope Effects ◽  
Kinetic Isotope ◽  
Leaving Group ◽  
Hydrolysis Of ◽  
Beta Galactosidase

scholarly journals The catalytic consequences of experimental evolution. Transition-state structure during catalysis by the evolved β-galactosidases of Escherichia coli (ebg enzymes) changed by a single mutational event

1989 ◽  
Vol 260 (1) ◽  
pp. 109-114 ◽  
Author(s):  
B F L Li ◽  
D Holdup ◽  
C A J Morton ◽  
M L Sinnott
Keyword(s):  
Transition State ◽  
Isotope Effects ◽  
Kinetic Isotope Effects ◽  
Mutational Event ◽  
Kinetic Isotope ◽  
Steady State Kinetic ◽  
Leaving Group ◽  
Enzyme Intermediates ◽  
Sugar Ring ◽  
Hydrolysis Of

1. The first chemical step in the hydrolysis of galactosylpyridinium ions by the evolvant ebg enzyme is less sensitive to leaving-group acidity than in the case of the wild-type ebg enzyme, implying less glycone-aglycone-bond fission at the transition state. 2. The first chemical step in the hydrolysis of aryl galactosides by ebg enzyme is probably less sensitive to leaving-group acidity than in the case of ebg enzyme, possibly as a consequence of resulting in more effective proton donation to the leaving aglycone. 3. alpha-Deuterium kinetic isotope effects of 1.1(0) and beta-deuterium kinetic isotope effects of 1.0(0) were measured for the hydrolysis of galactosyl-enzyme intermediates derived from ebg and ebg enzymes: these effects are not compatible with reaction of the sugar ring through a 4C1-like conformation, or with an ionic glycosyl-enzyme intermediate. 4. The variation with pH of steady-state kinetic parameters for hydrolysis of p-nitrophenyl galactoside by ebg and ebg enzymes and of 3-methylphenyl beta-galactoside, 3,4-dinitrophenyl beta-galactoside and beta-galactosyl-3-bromopyridinium ion by ebg enzyme was measured. The steep, non-classical, fall in activity against p-nitrophenyl galactoside at low pH observed with ebg and ebg enzymes is not observed with ebg enzymes.

Vinyl ether hydrolysis. XIII. The failure of I-strain to produce a change in rate-determining step

1980 ◽  
Vol 58 (2) ◽  
pp. 124-129 ◽  
Author(s):  
Y. Chiang ◽  
W. K. Chwang ◽  
A. J. Kresge ◽  
S. Szilagyi
Keyword(s):  
Vinyl Ether ◽  
Acid Catalysis ◽  
Isotope Effects ◽  
Kinetic Isotope Effects ◽  
Mineral Acid ◽  
Buffer Solutions ◽  
Rate Determining Step ◽  
Kinetic Isotope ◽  
Acetic Acid Buffer ◽  
Hydrolysis Of

Rates of hydrolysis of 1-ethoxy-3,3,5,5-tetramethylcyclopentene and 1-methoxy-2,3,3,5,5-pentamethylcyclopentene measured in mineral acid and formic and acetic acid buffer solutions show general acid catalysis and give large kinetic isotope effects in the normal direction (kH/kD > 1). This indicates that these reactions proceed by the conventional mechanism for vinyl ether hydrolysis in which proton transfer from the catalyzing acid to the substrate is rate-determining, and that the I-strain in these substrates is insufficiently great to shift the reaction mechanism to rapidly reversible substrate protonation followed by rate-determining hydration of the ensuing cationic intermediate.

ALPHA-SECONDARY DEUTERIUM KINETIC ISOTOPE EFFECTS FOR HYDROLYSIS OF TREHALOSE BY TREHALASE

2002 ◽  
Author(s):  
Jin-Ha Lee ◽  
Mamoru Nishimoto ◽  
Masayuki Okuyama ◽  
Haruhide Mori ◽  
Atsuo Kimura ◽  
...  
Keyword(s):  
Isotope Effects ◽  
Kinetic Isotope Effects ◽  
Kinetic Isotope ◽  
Hydrolysis Of

Transition-state structure for the hydronium-ion-promoted hydrolysis of α-d-glucopyranosyl fluoride

2015 ◽  
Vol 93 (4) ◽  
pp. 463-467 ◽  
Author(s):  
Jefferson Chan ◽  
Ariel Tang ◽  
Andrew J. Bennet
Keyword(s):  
Transition State ◽  
Kinetic Isotope Effect ◽  
Bond Cleavage ◽  
Isotope Effects ◽  
Kinetic Isotope Effects ◽  
Theoretical Modelling ◽  
Kinetic Isotope ◽  
Hydronium Ion ◽  
Anomeric Carbon ◽  
Hydrolysis Of

The transition state for the hydronium-ion-promoted hydrolysis of α-d-glucopyranosyl fluoride in water has been characterized by combining multiple kinetic isotope effect measurements with theoretical modelling. The measured kinetic isotope effects for the C1-deuterium, C2-deuterium, C5-deuterium, anomeric carbon-13, and ring oxygen-18 are 1.219 ± 0.021, 1.099 ± 0.024, 0.976 ± 0.014, 1.014 ± 0.005, and 0.991 ± 0.013, respectively. The transition state for the hydronium ion reaction is late with respect to both C–F bond cleavage and proton transfer.

Sign in / Sign up

Export Citation Format

Share Document