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