Effect of Fungicides on Fungus Enzymes

Abstract

EVIDENCE has already been obtained to show that an important mechanism of the toxic action of fungicides is the inhibition of fungus enzymes. Copper and mercury are known to inhibit different systems, including those concerned with carbohydrate metabolism¹. Rich and Horsfall² have investigated the action of phenols and quinones upon polyphenol oxidase, while Owens³ has examined the effect of organo-sulphur compounds, phenols, quinones and metal compounds upon amylases, polyphenol oxidase and catalase. Attention has been given to the mode of action of different types of derivatives of thiocarbamic acid. Weed, McCallan and Miller⁴ found that ferbam (ferric dimethyldithiocarbamate) inhibited urease, whereas nabam (disodium ethylene bisdithiocarbamate) had little effect. Sisler and Cox⁵ attribute the toxicity of thiram (bis(dimethylthiocarbamoyl) disulphide) largely to the inhibition of the enzyme triosephosphate dehydrogenase. The activity of 8-hydroxyquinoline has been ascribed⁶ to chelation with metal ions essential for enzyme action. Owens⁷ has shown that captan (N-trichloromethylthio-cyclcohex-4-ene-1,2-dicarboxyimide) prevents the assimilation of inorganic phosphate, and Hochstein, Cox and Sisler⁸ have reported that this compound affects cellular metabolism by blocking key decarboxylation reactions.