Effect of dicyclohexylcarbodiimide on unisite and multisite catalytic activities of the adenosine triphosphatase of Escherichia coli

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Abstract
The inhibitory effect of dicyclohexylcarbodimide (DCDD) on the activity of the ATPase of E. coli (ECF1) was examined in detail. DCCD reacted with ECF1 predominantly in .beta. subunits with a maximum of 2 mol of reagent/mol of .eta.F1 being incorporated in these subunits. Of steady-state or multistate ATPase activity, 95% inhibition required incorporation of 1 mol DCCD/inhibition mole of enzyme into .beta. subunits. Of the intial rate of unisite catalysis, 75% inhibition was only obtained after incorporation of 2 mol of DCCD/mole of ECF1 into .beta. subunits. Analyses of the kinetics of unisite catalysis and nucleotide binding experiments both indicate that DCCD binds outside the substrate ATP binding site. Inhibition by this reagent appears to be due in part to an effect on the catalytic sites but mainly to the blocking of cooperativity between these sites.

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