Metal Ion Activator on Intrinsic Isotope Effects of Hydride Transfer and Decarboxylation in the Reaction Catalyzed by the NAD-Malic Enzyme from Ascaris suum

Biochemistry ◽  
1995 ◽  
Vol 34 (10) ◽  
pp. 3253-3260 ◽  
Author(s):  
William E. Karsten ◽  
Sandya R. Gavva ◽  
Sang-Hoon Park ◽  
Paul F. Cook
Keyword(s):  
Malic Enzyme ◽  
Metal Ion ◽  
Ascaris Suum ◽  
Isotope Effects ◽  
Hydride Transfer

scholarly journals The role of enzyme dynamics and tunnelling in catalysing hydride transfer: studies of distal mutants of dihydrofolate reductase

2006 ◽  
Vol 361 (1472) ◽  
pp. 1307-1315 ◽  
Author(s):  
Lin Wang ◽  
Nina M Goodey ◽  
Stephen J Benkovic ◽  
Amnon Kohen
Keyword(s):  
Temperature Dependence ◽  
Dihydrofolate Reductase ◽  
Isotope Effects ◽  
Hydride Transfer ◽  
Activation Parameters ◽  
Physical Nature ◽  
Enzyme Dynamics ◽  
Temperature Dependences ◽  
Donor Acceptor ◽  
Significant Temperature

Residues M42 and G121 of Escherichia coli dihydrofolate reductase ( ec DHFR) are on opposite sides of the catalytic centre (15 and 19 Å away from it, respectively). Theoretical studies have suggested that these distal residues might be part of a dynamics network coupled to the reaction catalysed at the active site. The ec DHFR mutant G121V has been extensively studied and appeared to have a significant effect on rate, but only a mild effect on the nature of H-transfer. The present work examines the effect of M42W on the physical nature of the catalysed hydride transfer step. Intrinsic kinetic isotope effects (KIEs), their temperature dependence and activation parameters were studied. The findings presented here are in accordance with the environmentally coupled hydrogen tunnelling. In contrast to the wild-type (WT), fluctuations of the donor–acceptor distance were required, leading to a significant temperature dependence of KIEs and deflated intercepts. A comparison of M42W and G121V to the WT enzyme revealed that the reduced rates, the inflated primary KIEs and their temperature dependences resulted from an imperfect potential surface pre-arrangement relative to the WT enzyme. Apparently, the coupling of the enzyme's dynamics to the reaction coordinate was altered by the mutation, supporting the models in which dynamics of the whole protein is coupled to its catalysed chemistry.

Multiple isotope effects with alternative dinucleotide substrates as a probe of the malic enzyme reaction

Biochemistry ◽  
1991 ◽  
Vol 30 (23) ◽  
pp. 5755-5763 ◽  
Author(s):  
Paul M. Weiss ◽  
Sandhya R. Gavva ◽  
Ben G. Harris ◽  
Jeffrey L. Urbauer ◽  
W. W. Cleland ◽  
...  
Keyword(s):  
Malic Enzyme ◽  
Isotope Effects ◽  
Enzyme Reaction

Determination of the Chemical Mechanism of Malic Enzyme by Isotope Effects†

Biochemistry ◽  
1997 ◽  
Vol 36 (5) ◽  
pp. 1141-1147 ◽  
Author(s):  
William A. Edens ◽  
Jeffrey L. Urbauer ◽  
W. W. Cleland
Keyword(s):  
Malic Enzyme ◽  
Isotope Effects ◽  
Chemical Mechanism
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