Enzymatic hydrolysis of organophosphate insecticides, a possible pesticide disposal method

Abstract

A crude cell extract from a mixed bacterial culture growing on parathion, an organophosphate insecticide, hydrolyzed parathion (21 C) at a rate of 416 nmol/ min per mg of protein. This rate of enzymatic hydrolysis, when compared with chemical hydrolysis by 0.1 N sodium hydroxide at 40 C, was 2,450 times faster. Eight of 12 commonly used organophosphate insecticides were enzymatically hydrolyzed with this enzyme preparation at rates ranging from 12 to 1,360 nmol/ min per mg of protein. Seven pesticides were hydrolyzed at rates significantly higher (40 to 1,005 times faster) than chemical hydrolysis. The pH optimum for enzymatic hydrolysis of the eight pesticides ranged from 8.5 to 9.5, with less than 50%o of maximal activity expressed at pH 7.0. Maximal enzyme activity occurred at 35 C. The crude extract lost its activity at the rate of only 0.75%/day when stored at 6 C. Eight organic solvents, ranging from methanol to hexane, at low concentrations stimulated enzymatic hydrolysis by 3 to 20%, whereas at higher concentrations (1,000 mg/liter) they inhibited the reaction (9 to 50%). Parathion metabolites p-nitrophenol, hydroquinone, and diethylthiophosphoric acid, at up to 100-mg/liter concentrations, did not significantly influence enzyme activity.

Microbial degradation of organophosphorus compounds

“…Bioremediation with micro-organisms is therefore an at-tractive alternative to these conventional techniques for pollutant disposal. Munneck (1976) first reported the potential use of parathion hydrolase producing bacteria for the detoxification and disposal of organophosphorus compounds. Later, successful use of OPH producing bacteria for complete destruction of coumaphos in cattle-dip waste was reported Karns et al, 1987).…”

Microbial metabolism of sulfurand phosphorus-containing xenobiotics

“…[47,48]). These include species of Flat'obacterium [49], Arthrobacter [50], and Pseudomonas [51][52][53][54], as well as many isolates which were not further identified [55][56][57]. In principle, parathion and malathion may also provide both sulfur and phosphorus for growth, but research into this aspect of organophosphate degradation has been much less extensive.…”

“…Parathion [55,57,58] or to provide phosphorus for growth [59]. The enzyme that catalyses the hydrolysis is a phosphotriesterase (aryldialkylphosphatase, EC 3.1.8.1).…”

“…Phosphotriesterase in strain B-1 was found to be a cytosolic, 43-kDa enzyme, while in strain SC the enzyme consisted of four identical 67 kDa subunits [56]. Phosphotriesterase catalyses a single hydrolysis of arylphosphotriesters to the dialkyl ester products, and accepts a broad range of aryldialkylphosphotriesters as substrate [57,63], including both phosphate esters and phosphorothionates [57]. The phosphotriesterase enzymes found in P. diminuta and Flavobacterium sp.…”

Hydrolysis of Selected Organophosphorus Insecticides by Two Bacteria Isolated from Flooded Soil

“…Not all phosphorothioates with a common P-0-C linkage were hydrolysed with ease by a crude enzyme from a mixed bacterial culture (Munnecke 1976). Thus, diethyl phosphorothioates, parathion and diazinon, were readily hydrolysed by this enzyme despite differences in the ring moiety; but the dimethyl phosphorothioate, methyl parathion, with the same ring moiety as parathion was somewhat resistant to enzymatic hydrolysis.…”