Soman-hydrolyzing and -detoxifying properties of an enzyme from a thermophilic bacterium.

An enzyme that hydrolyzes soman (1,2,2-trimethylpropyl methylphosphonofluoridate) and two other phosphonofluoridates, but does not hydrolyze DFP (diisopropylphosphorofluoridate), has been partially purified from a rod-shaped spore-forming gram-positive OT (obligate thermophilic) bacterium. The enzyme shows a marked Mn2+ stimulation, and in this and its substrate preference does not resemble the organophosphorus acid anhydrolase (sometimes termed DFPase) found in squid. Like the squid enzyme, it is not inhibited by mipafox (N,N'-diisopropylphosphordiamidofluoridate), is not inactivated by ammonium sulfate, and does hydrolyze the acetylcholinesterase-inhibitory pair of diastereoisomers of soman as well as the relatively noninhibitory pair, thus detoxifying soman. In these three properties the OT enzyme does not resemble the ubiquitous organophosphorus acid anhydrolase often purified from mammalian and bacterial sources by cold ethanol fractionation. Thus this phosphono-specific OT enzyme may have a natural substrate and a physiological role distinct from other organophosphorus acid anhydrolases.