Phorate sulfoxidation by plant root extracts

Abstract

Soybean root homogenates were found to oxidize phorate to phorate sulfoxide. Neither PO nor sulfone derivatives of phorate were detected. Fractionation of soybean root homogenate indicates that the enzyme(s) which oxidize phorate to the sulfoxide are largely (72%) in the 25,000 g pellet. In vitro studies of the 25,000 g pellet indicate a linear reaction rate at 34°C for periods of up to 2 h at the pH optimum of 5.5. Soybean and bean root 25,000 g pellets were twice as active on a mg protein basis as those from barley, corn, wheat, sorghum and over ten times more active than tomato. In vitro studies indicate that Counter, disulfoton, fenthion, aldrin, heptachlor, piperonyl butoxide, sulfoxide, atrazine, SKF525A and p-chlorothioanisole when present at a 10:1 ratio with phorate significantly inhibited soybean root phorate sulfoxidation.