QSARS OF ANTI-FUNGAL ACTIVITY OF FURAN CARBOXANILIDE DERIVATIVES AGAINST WILD AND MUTANT STRAINS OF USTILAGO MAYDIS

The structural requirements for the inhibitor activity of various furan carboxanilide derivatives against succinate dehydrogenase complex (SDC) activity in mitochondria of either wild or mutant strains of Ustilago maydis were investigated with the aid of Hansch QSAR analysis. It has been found that the inhibitor activity against both types of enzymes is best related to the ??? or ??M of the substituents on the phenyl ring and to the hydrophobicity of substituents at ortho (with negative slope) and meta position (with positive slope). Similarly, the activity- decreases with the increase in the width of substituents at ortho position. However, while the activity decreases with the increase in the width of substituents at para position of phenyl ring for the wild type enzyme, the reverse is true for the mutant type enzyme. Moreover, in spite of wild type enzyme, the activity against mutant type enzyme 'is related to the presence of a hydrogen acceptor group at meta position of the phenyl ring. These data indicate that the difference between wild and mutant types of SDC enzymes in the U. maydis has been brought about by the appearance of an amino acid residue with the ability to form hydrogen binding in the active site of the mutant enzyme