Kinetics of the DFPase Activity in <i>Tetrahymena thermophila</i>¹

Abstract

Crude homogenates of the ciliate protozoon, Tetrahymena thermophila, can hydrolyze the potent acetylcholinesterase inhibitors O,O-diisopropylphosphorofluoridate (DFP) and O-1,2,2-trimethylpropylmethylphosphonofluoride (soman). Characterization of the enzymatic activity of the homogenate has been performed. The DFPase operates over a pH range of 4 to 10 and an ionic range of 0-500 mM NaCl. Rate of reaction increases three- to four-fold from 25 degrees C to 40 degrees C and is still present at 55 degrees C. These results indicate that the enzymatic activity operates over a broad range of environmental conditions, making it an attractive material for use in the detoxification and detection of organofluorophosphates. DFPases may be important in the metabolism of naturally occurring organophosphates.