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A membrane-bound inositol phospholipid-specific phospholipase C was solubilized from rice (Oryza sativa L.) microsomal membranes and purified to apparent homogeneity using a series of chromatographic separations. l h e apparent molecular mass of the enzyme was estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis to be 42,000 D, and the isoelectric point was 5

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The two insecticidal peptides Bm32-VI and Bm33-I, isolated from the venom of the Chinese scorpion Buthus martensi induce paralytical symptoms typical of insect contractive toxins. They show, respectively, 74% and 77% homology with AaIT from Androctonus australis, comparable insecticidal activity and no vertebrate toxicity. Under voltage-clamp conditions, both toxins induced (1) an increased fast Na + current, (2) a shift in voltage dependence of Na + current activation, (3) the occurrence of a delayed current, and (4) a slow development of a holding current. Increased Na + conductance at negative potential values is responsible for axonal hyperexcitability and the contractive paralysis of insect prey. ß

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