ABSTRACT
When a nerve gas hydrolyzing enzyme [organophosphorus acid anhydrolase (OPAA), formerly DFPase] purified from squid hepatopancreas was injected into rabbits, the resulting sera (RAS) inhibited OPAA purified from either squid hepatopancreas or squid optic ganglia. The inhibition was non-competitive, with 50% inhibition at a 1:1,000 serum dilution, and with the limit of inhibition (in effect, a "titer") at approximately 1:10,000. This RAS did not inhibit the distinctly different OPAAs from a mammalian and two bacterial sources. The hepatopancreas-generated RAS also reacted positively to the appropriate enzyme-linked immunosorbent assay (ELISA) at a titer of 1:100,000. In marked contrast, when OPAA purified from squid optic ganglion was injected into rabbits, the resulting sera did not inhibit squid OPAA, and did not give a positive ELISA. Control sera taken from the same rabbits prior to any injection (RS) did not inhibit the OPAAs. These results show another major difference between squid type OPAAs and the OPAAs from other sources, sometimes termed "Mazur type" OPAAs.
Subject(s)
Decapodiformes/enzymology , Esterases/isolation & purification , Immune Sera/immunology , Phosphoric Triester Hydrolases , Animals , Antibody Specificity , Aryldialkylphosphatase , Enzyme-Linked Immunosorbent Assay , Escherichia coli/enzymology , Esterases/immunology , Geobacillus stearothermophilus/enzymology , Isoflurophate/metabolism , Liver/enzymology , Mathematics , Pancreas/enzymology , Rabbits , Soman/metabolism , SwineABSTRACT
Three organophosphorus acid anhydrases have been isolated from E. coli by gel filtration and ion exchange column procedures, and further identified by gel electrophoresis. All three have molecular weights in the 120,000-140,000 range. Two of them hydrolyze racemic 1,2,2-trimethylpropylmethylphosphonofluoridate (soman) to completion at a single rate and, in parallel with this, detoxify soman at a comparable rate. The third enzyme appears to show stereoselectivity with respect to the two pairs of isomers of soman in that it hydrolyzes the racemic mixture at a fast and a slow rate, the latter approaching the non-enzymatic rate, and detoxifies soman only at the slower rate. In the past, organophosphorus acid anhydrases from bacterial and mammalian sources have been assayed either as crude sonicates or homogenates, or as cold ethanol precipitated fractions. Major discrepancies among laboratories have probably been due either to the assay of mixtures of varying proportions of these three enzymes depending on the various organs or organisms used as the source, or to the purification of one of the enzymes at the expense of the others. For E. coli, a fourth organophosphorus acid anhydrase is also present but at a considerably lower activity.
