Degradation of organophosphates by fish liver phosphatases

Liver homogenates of bluegill, Lepomis macrochirus Rafinesque, and channel catfish, Ictalurus punctatus (Walbaum), were shown by a manometric technique to contain soluble enzymes capable of degrading diisopropyl phosphorofluoridate (DFP) and 2,2-dichlorovinyl dimethyl phosphate (dichlorvos). Hydrolysis of the compounds was greatest in the presence of the manganic ion. Tentative identification of certain of the hydrolysis products suggested that cleavage of the anhydride bond was a degradation pathway for DFP and dichlorvos in vitro under the assay conditions employed. Substrate summation, inhibition, and activation experiments failed to clearly indicate more than a single enzyme hydrolyzing DFP and dichlorvos in the two fish.