Detoxification of organophosphate pesticides using a nylon based immobilized phosphotriesterase from Pseudomonas diminuta.
A partially purified phophotriesterase was successfully immobilized onto nylon 6 and 66 membranes, nylon 11 powder, and nylon tubing. Up to 9000 U of enzyme activity was immobilized onto 2000 cm2 of a nylon 6 membrane where 1 U is the amount of enzyme necessary to catalyze the hydrolysis of 1.0 mumol of paraoxon/min at 25 degrees C. The nylon 66 membrane-bound phosphotriesterase was characterized kinetically where the apparent Km value for the immobilized enzyme was 0.35 mM. This is 5-6 times higher than that observed for the soluble enzyme. However, nylon immobilization limited the maximum rate of paraoxon hydrolysis to less than 10% of the value measured for the soluble enzyme. The addition of the cosolvent, methanol, resulted in an increase in the apparent Km value for paraoxon hydrolysis but concentrations up to 40% had no negative effect on the catalytic effectiveness with the soluble or immobilized phosphotriesterase. Based on the kinetic analysis, methanol appears to be a competitive inhibitor for both forms of enzyme. The nylon powder immobilized enzyme was shown to be stable for at least 20 mo. The immobilization of the phosphotriesterase onto nylon provides a practical method for the detoxification of organophosphate pesticides.
Caldwell
S R
SR
Department of Biochemistry, Texas A&M University, College Station 77843.
Raushel
F M
FM
D043303:Aryldialkylphosphatase; D004795:Enzyme Stability; D004800:Enzymes, Immobilized; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D007700:Kinetics; D009757:Nylons; D010261:Paraoxon / Q000737:chemistry*; D010744:Phosphoric Monoester Hydrolases / Q000737:chemistry*; D011549:Pseudomonas / Q000201:enzymology
D004800:Enzymes, Immobilized; D009757:Nylons; D010744:Phosphoric Monoester Hydrolases; D043303:Aryldialkylphosphatase; D010261:Paraoxon