Organophosphate degrading enzymes in the crude supernatant fraction from the rat liver

Abstract

Attempts were made to classify the enzymes which degrade insecticidal organophosphates in the crude supernatant fraction (i.e. 20,000 X g supernatant) of the rat liver. On the basis of cofactor and ion activation characteristics of the enzymes, four distinctly different types of enzymes have been observed. The enzymes which degraded malathion and parathion were detected by the electrophoresis method. Electrophoresis treatments did not, however, facilitate the detection of Ca2+ or GSHstimulated enzymes. Most of the esterases detected in the rat liver 20,000 X g supernatant by using 1-naphthyl acetate do not appear to play any significant role in degrading organophosphates.There are two major groups of enzyme systems known to degrade toxic organophosphorus esters in the rat liver: the microsomal oxidative system and nonoxidative enzymes such as esterases and dealkylating enzymes. While the former has been the subject of recent intensive studies, the latter group of enzymes has only been examined by a relatively few workers. Examples of such works are described in the papers by Mounter (1955) on DFPase, by Hodgson and Casida (1962) and by Main and Braid (1962) on malathion hydrolyzing aliesterase, by Fukami and Shishido (1963) and Shishido and Fukami (1963) on dealkylating enzymes for dimethyl organophosphates, by Suwanai and Shishido (1965) and Yang et al. ( 1971) on diazinon degrading enzymes, and by Kojima and O'Brien (1968) on paraoxon degrading enzymes. In brief, from the above works there appears to be at least several types of such enzymes: an esterase degrading

Review: Can Toxic Substances Initiate Psychotic Behavior? Part II. Organophosphate (OP) Substances with Anti-Acetylcholinesterase Enzyme Activity

“…Many toxic OPs as diazinon containing a sulfur atom undergo oxidation to oxons [17]- [22], and their biotransformation yields substances with increased toxicity. Parathion has an analogous ability to be oxidized to paraoxon and yield more toxic oxons [23]- [25] (Scheme 2). The reactions of transformation and biotransformation of phosphorothioates to the corresponding (more toxic) oxons are common among all members of this family of substances, and can be supported by examples of important phosphorothioates: salithion [26] and cyanox [27].…”

Degradation of Malathion and Phenthoate by Glutathione Reductase in Wheat Germ

“…Some investigators have shown that bacterial enzymes cause degradations of several organophosphorothioates such as malathion (Lai et al, 1998). Although many cases of enzymatic degradation of organophosphorus pesticides by mammal (Menn et al, 1996;Miyata and Matsumura, 1972) or insect (Severini et al, 1997;Campbell et al, 1997;Wood et al, 1986;Wool et al, 1982) enzymes have been studied, those by plant enzyme have not been as extensively studied (Bedi and Roy, 1979).…”

Metabolism of parathion in perfused whole pig livers

“…gated (Appleton and Nakatsugawa, 1977;Fuhremann et al, 1974;Gaines et al, 1966;Ku and Dahm, 1973;Lichtenstein et al, 1973;Miyata and Matsumura, 1972;Nakatsugawa and Dahm, 1967;Nakatsugawa et al, 1968Nakatsugawa et al, , 1969Neal, 1967a,b;Neal and DuBois, 1965;Pankaskie et al, 1952;Whitehouse and Ecobichon, 1975) and reviewed (Schoenig, 1975). These studies have revealed an ^ vivo metabolic manipulation of parathion via two pathways (Figure 1).…”