Characterization of a DFP-hydrolyzing enzyme in squid posterior salivary gland by use of Soman, DFP and manganous ion.

1. A phosphorus-fluorine splitting enzyme (DFPase) from squid nerve hydrolyzes DFP 5-10 times faster than it hydrolyzes another P-F compound, Soman, whereas a superficially similar enzyme from rat kidney hydrolyzes Soman 20-40 times faster than it hydrolyzes DFP, all under comparable conditions. 2. The DFPase from rat kidney is stimulated 2- to 3-fold by 4 X 10(-4) M Mn2+, whereas the DFPase from squid nerve is unaffected or slightly inhibited by 4 X 10(-4) M Mn2+. 3. These observations form the basis for distinguishing between a squid type DFPase and a mammalian DFPase, the names not being rigorously indicative of enzyme source or substrate. 4. When these criteria are applied to a P-F splitting enzyme found in squid saliva, the enzyme is identifiable as squid type DFPase. There is a significantly higher level of this enzyme in whole saliva from female squids than in whole saliva from male squids. This squid type DFPase is different from the proteinous toxin also found in squid saliva.