Characterization of a soluble mouse liver enzyme capable of hydrolyzing diisopropyl phosphorofluoridate

A novel mouse liver soluble fraction DFPase which has organophosphatase act ivities with sarin, soman and tabun, was purified and characterized. Howeve r, it lacks paraoxonase and arylesterase activities with paraoxon and pheny l acetate, respectively. This DFPase closely resembles and may be identical with the one purified by Little et al. in 1989 from the soluble fraction o f rat liver, based on its substrate specificity, size (similar to 39 kDa) a nd its stimulation by several metal ions, namely magnesium, manganese and c obalt. Sequencing of our purified mouse liver DFPase showed it to be identi cal in its amino acid sequence with the recently identified senescence mark er protein-30 (SMP-30) by Fujita et al. in 1996. Other senescence marker pr oteins possessing high structural homology with the mouse SMP-30 have also been found and sequenced from human and rat livers. There is no structural homology between the senescence marker protein family and the group of mamm alian paraoxonases. Thus,it is clear that there are at least two distinct, unrelated families of mammalian liver enzymes that share DFPase activity. ( C) 1999 Elsevier Science Ireland Ltd. All rights reserved.