Document Detail

Mechanism from isotope effects.
MedLine Citation:
PMID:  9854842     Owner:  NLM     Status:  MEDLINE    
Isotope effects represent perhaps one of the most versatile tools available to investigators interested in the determination of reaction mechanism, particularly in the case of the mechanistic enzymologist. Interpretation of isotope effect data is somewhat more difficult for enzyme reactions, since the chemical or isotope-dependent step(s) is(are) normally not solely rate-limiting as they are for non-enzyme-catalyzed reactions. One can, however, take advantage of rate-limitation by multiple steps in an enzyme-catalyzed reaction to obtain information on a number of aspects of mechanism. In this paper, simple theory for the application of isotope effects to reaction mechanism is developed, and applied to organic reactions and those catalyzed by enzymes. Techniques used to measure isotope effects depend somewhat on the isotope used, that is radioisotope vs. stable isotope, or hydrogen isotope vs. heavier atoms. Techniques to be discussed include competitive and noncompetitive (or internal discrimination) measurements. In enzyme-catalyzed reactions, information can be obtained on the order of addition of reactants and relase of products, and this will be illustrated using the 6-phosphogluconate and alcohol dehydrogenase reactions. The use of multiple isotope effects can be used to distinguish between stepwise and concerted reactions, and this will be illustrated with the formate and glucose 6-phosphate dehydrogenase and malic enzyme reactions.
P F Cook
Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, P.H.S.; Review    
Journal Detail:
Title:  Isotopes in environmental and health studies     Volume:  34     ISSN:  1025-6016     ISO Abbreviation:  Isotopes Environ Health Stud     Publication Date:  1998  
Date Detail:
Created Date:  1999-01-28     Completed Date:  1999-01-28     Revised Date:  2008-11-21    
Medline Journal Info:
Nlm Unique ID:  9602611     Medline TA:  Isotopes Environ Health Stud     Country:  NETHERLANDS    
Other Details:
Languages:  eng     Pagination:  3-17     Citation Subset:  IM    
Department of Chemistry and Biochemistry, University of Oklahoma, Norman 73072, USA.
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MeSH Terms
Alcohol Dehydrogenase / metabolism
Chemistry, Organic
Enzymes / metabolism*
Formate Dehydrogenases / metabolism
Glucosephosphate Dehydrogenase / metabolism
Malate Dehydrogenase / metabolism
Models, Chemical*
Organic Chemistry Phenomena
Phosphogluconate Dehydrogenase / metabolism
Grant Support
Reg. No./Substance:
0/Enzymes; 0/Isotopes; EC Dehydrogenase; EC Dehydrogenase; EC dehydrogenase-(oxaloacetate-decarboxylating) (NAD+); EC Dehydrogenase; EC Dehydrogenase; EC Dehydrogenases

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