INHIBITION OF THE ESTERATIC ACTIVITY OF THROMBIN BY SARIN AND TABUN

Abstract

Isopropyl methylphosphonofluoridate (sarin) and ethyl N,N-dimethylphosphoramidocyanidate (tabun) have been found to inhibit the esteratic activity of thrombin towards the substrate p-toluenesulphonyl-L-arginine methyl ester. The rate of inhibition is markedly dependent on pH and is greatest in alkaline solutions. At pH 7.8 and 25 °C, the specific rate for inhibition by tabun at a concentration of 6.17 × 10−4 M is 0.0271 minutes−1and for sarin at a concentration of 7.15 × 10−5 M it is 0.0232 minutes−1. Thrombin which is completely inhibited by sarin could not be reactivated by use of oximes at pH 9 and concentrations of 0.02 M.