RATE OF ISOTOPE EXCHANGE IN ENZYNE-CATALYZED REACTIONS

被引:41
作者
YAGIL, G
HOBERMAN, HD
机构
[1] Department of Cell Biology, Weizmann Institute of Science, Rehovoth
[2] Department of Biochemistry, Albert Einstein College of Medicine, Bronx
关键词
D O I
10.1021/bi00829a049
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
The methodology of treating the kinetics of isotope exchange catalyzed by enzymes is discussed. A relatively simple way of deriving the equations relating velocity at equilibrium of an enzymatic reaction with the kinetic parameters of the reaction is described. The following general relations are helpful. The equilibrium rate of n consecutive reactions is given by [formula omitted] The equilibrium rate of n parallel reactions is [formula omitted] These relations also make possible the calculation of exchange rates through coupled enzymatic reactions which occur in metabolizing systems. In the experimental part the rate of tritium equilibration between position 4A of reduced nicotinamide-adenine dinucleo-tide and position 2 of L-lactate is measured. Series of measurements in which lactate is varied between 0.37 and 37 mM at constant pyruvate and reduced nicotinamide-adenine dinucleotide concentrations, as well as series in which pyruvate is varied between 4.3 and 86 μm at constant lactate and pyruvate concentrations, are reported. The results, in conjunction with the equations derived in the first part, make possible the evaluation of three rate constants involved in the lactate dehydrogenase reaction. These constants are summarized in Table II, and are shown to be close to the ones obtained from initial rate studies. © 1969, American Chemical Society. All rights reserved.
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页码:352 / &
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