STUDIES ON THE INHIBITING ACTION OF PCMB TO ARGINASE USING MICROCALORIMETRY

Microcalorimetry was used to study the inhibiting action of p-chlorome r-curibenzoic acid (PCMB) to L-arginine hydrolysis with arginase. PCMB was determined as a competitive irreversible inhibitor and the second -order rate constant of the reaction between PCMB and arginase was K-0 = 92.17 L/(mol . s) at 298.15 K and pH 9.4. The properties of the ac tive site of arginase were investigated by using PCMB as a modifying a gent. The results of chemical modification reveal that arginase contai ns 3 reactive cysteinyl residues at most but these residues do not bel ong to the active site of arginase. The modification of 3 cysteinyl re sidues by PCMB led to similar to 50% inhibition of arginase activity.