Carboxylesterases in guinea-pig plasma and liver. Tissue specific reactivation by diacetylmonoxime after soman inhibition in vitro.

The carboxylesterase activity in both plasma and liver of guinea-pig were separated into three main peaks by chromatofocusing. Two of the three plasma enzymes were retained by affinity chromatography on Affi-Gel Blue (100-200 mesh). Isoelectric points determined by chromatofocusing or isoelectrofocusing were pI 6.1, pI 5.2 and pI 4.0 for the plasma enzymes, and pI 5.7, pI 5.2 and pI 4.5 for the liver enzymes. The effect of selective esterase inhibitors, soman, physostigmine (cholinesterase inhibitor) and bis-4-nitrophenyl phosphate (carboxylesterase inhibitor), suggested that the three enzymes in both tissues may be regarded as carboxylesterases. However, the pI 5.7 carboxylesterase was partially inhibited by physostigmine, and the pI 4.5 carboxylesterase was almost not affected by bis-4-nitrophenyl phosphate. The ratio between the activities towards 4-nitrophenyl butyrate and methyl butyrate differed among the carboxylesterases in both tissues. All three carboxylesterases in plasma were partially reactivated by diacetylmonoxime after soman inhibition in vitro, but to a different extent. The soman inhibited liver carboxylesterases were not reactivated by diacetylmonoxime.