Formyltetrahydrofolate Synthetase
A STUDY OF EQUILIBRIUM REACTION RATES
Barbara K. Joyce 1 and Richard H. Himes 1
From the
1 From the Department of Microbiology and the Department of Comparative Biochemistry and Physiology, University of Kansas, Lawrence, Kansas 66044
The equilibrium reaction rates of the formyltetrahydrofolate synthetase reaction catalyzed by the crystalline enzyme from Clostridium cylindrosporum were determined by measuring the rates of exchange at equilibrium of formate 
10-formyltetrahydrofolate, orthophosphate adenosine triphosphate, and ADP ATP. The effects of increasing the concentrations of the reactant pairs ADP and ATP, Pi and ATP, formate and 10-formyltetrahydrofolate, and tetrahydrofolate and 10-formyltetrahydrofolate were examined. The results were not consistent with an ordered addition of substrates, but were explained by a random mechanism. In addition, the results indicate that in some cases the binding of a substrate to the enzyme is affected by the presence of other substrates. The absence of a large difference between the exchange rates when all reactants are present in saturating concentrations suggests that the rate of interconversion of the quaternary complexes and the rates of dissociation of all the reactants from the enzyme are of the same order of magnitude.
Submitted on May 26, 1966
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