[Inhibition of mitochondrial ATPase by water-soluble carbodiimide]

Modification of the carboxyl group with pK 6,8-7,0 of isolated factor F1 by N-cyclohexyl-N'-beta-(4-xethylmorpholine) ethylcarbodiimide (CMCD) leads to the inhibition of the ATPase activity of the enzyme. The reaction rate of factor F1 with CMCD drops in the presence of ATP. It has been shown that during the first stage of the reaction reversible binding of CMCD with factor F1 occurs, forming a stable "enzyme--inhibitor" complex (Kdis=2.10(-4) M). N-cyclohexyl-N'-beta-(4-methylmorpholine) ethylcarbamide, a close analog of CMCD, is a competitive inhibitor of the ATPase reaction with Ki=9.10(-4) M. It is assumed that the carboxyl group, which reacts with CMCD, is located in the catalytic site of factor F1 and serves as the ligand of Me2+ in binding the substrate of the ATPase reaction Me-ATP. The reaction of factor F1, which was modified by CMCD, with proflavine, is accompanied by the covalent binding of the fluorescent label to the enzyme. The binding of proflavine to factor F1 leads to a sharp drop in the solubility of the enzyme in water.