Abstract
Microsomal preparations from mycelial cells of a strain of Pyricularia oryzae designated as P-2 cleaved the P-S or S-C bonds in phosphorothiolate ester linkage of IBP (S-benzyl O, O-diisopropyl phosphorothiolate, Kitazin P®) and formed diisopropyl phosphate (DIP) and diisopropyl phosphorothioate (DIPT). When the test fungus was cultured in the presence of phenobarbital, it strongly induced the formation of DIP, however the induction of DIPT formation by phenobarbital was weak in this experiment with a cell-free system. The cleavage reactions of P-S and S-C bonds require NADPH and oxygen for activity. Reduced microsomal preparations, when treated with carbon monoxide, showed maxima at 450 and 420nm. The inhibitors of mixed function oxidase, SKF-525A, piperonyl butoxide and carbon monoxide, and electron acceptors, cytochrome c and 2, 6-dichloroindophenol, suppressed the formation of DIP and DIPT. These results revealed the participation of mixed function oxidase in the cleavage of P-S and S-C bonds in IBP by mycelial cells of P. oryzae.
