Purification and properties of soman-hydrolyzing enzyme from human liver

A soman-hydrolyzing enzyme (soman-ase) was purified from human liver. The humansomanase is capable of hydrolyzing pinacolyl meth-ylphosphonofluoridate (soman), diisopropylphos-phorofluoridate (DFP), and ethyl-N-dimethyl phos-phoramidocyanidate (Tabun) with P–F or P–CNbonding, but not ethyl (S-2-diisopropylaminoethyl)methylphosphonothiolate (VX) and diethyl-p -nitro-phosphenylphosphate (paraoxon) with P–S or P–O bonding. The somanase has been purified 1570-fold with a specific activity of 41.4 μmol/min/mg protein. Its molecular weight is around 58 kDa determined by SDS-PAGE. The somanase could be stimulated by the divalent cations Mn⁺², Mg⁺², and Co⁺², where Co⁺² activation is the highest. The requirement of disulfide bonds for the enzyme activity was demonstrated by the inhibition effect of DTT. © 1998 John Wiley & Sons, Inc. J Biochem Toxicol 12: 213–217, 1998