MALATHION CARBOXYLESTERASE ACTIVITY IN HUMAN-LIVER AND ITS INACTIVATION BY ISOMALATHION

Malathion carboxylesterase activity was assayed in 16 samples of human liver obtained at autopsy. In general, this survey did not suggest correlations between malathion carboxylesterase activity and age, sex, or cause of death. However, the lowest levels of carboxylesterase activity were found in two severely steatotic livers and one cholestatic liver, indicating a possible relationship between liver pathology and its capacity to detoxify malathion. A soluble stable and partially purified preparation of human liver malathion carboxylesterase was obtained by detergent extraction and fraction of whole liver homogenate. The activity of this fraction was susceptible to concentration-dependent inactivation by isomalathion but was resistant to three other impurities isolated from technical malathion. The potency of isomalathion as a malthion carboxyl-esterase inactivator supports the possibility that this compound may have contributed to the recently reported epidemic of malathion poisonings in Pakistan. © 1979.