Abstract
The inhibition of lactate dehydrogenase at high pyruvate concentration was studied in three ways. First, a rapid decrease in the rate of the enzyme reaction was observed; secondly, the rate of formation of a pyruvate–NAD+ compound was followed by the change in E325; thirdly, the rate of quenching of the protein fluorescence was measured. The data obtained at pH6·0 at different temperatures and ionic strengths as functions of pyruvate, NAD+ and enzyme concentrations show that the extent of inhibition can be correlated with the reversible formation of a compound between pyruvate and enzyme-bound NAD+. It is suggested that the detailed kinetic analysis of the formation of this abortive ternary compound will give pertinent information about properties of the enzyme–NAD+ compound involved in the normal catalytic process.
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Selected References
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