MICROCALORIMETRY APPLIED TO THE STUDY OF PRODUCT INHIBITION OF SINGLE- SUBSTRATE ENZYME - CATALYZED-REACTIONS

Reduced extent equations for kinetics of single - substrate product - inhibited enzyme - catalyzed reactions and mathematical model for ther mokinetics have been suggested. By analyzing the thermograms of these reactions, this model can be conveniently used to calculate both kinet ic parameters (K-m, K-i and V-m) and molar enthalpy (Delta(r)H(m)), an d to establish the type of product inhibition simultaneously. Thermoki netics of arginase - catalyzed hydrolysis of L - arginine was studied by microcalorimetry, and the reaction product, L - ornithine, was esta blished as a competitive reversible inhibitor. At 298.15K and pH 9.4, the K-i value for L - ornithine was 1.22 x 10(-3)mol . L(-1). The reli ability of this method for thermokinetics of single - substrate produc t - inhibited enzyme - catalyzed reactions has been verified by the ex perimental results.