The influence of Z-4,4-bis(4-ethylphenyl)-2,3-dibromo-2-butenoic acid, the compound originally synthetized as a cytostatic edikron and showing inhibitory effect on several pyridoxal enzymes, on absorption and circular dichroism spectra of alanine and aspartate aminotransferases (ALT, AST) in the region of coenzyme absorption characteristics was studied. In the case of AST, the compound decreased absorption and CD maxima at 360 nm, which represents the active form of the enzyme, but it did not seem to prevent formation of the pyridoxamine form of the enzyme, produced in the presence of L-aspartate. Edikron caused insignificant spectral changes of ALT, but it partially denatured the enzyme. Circular dichroism measurement of both enzymes uncovered some effects of edikron at 250-300 nm, which suggests conformational changes in the aromatic amino acids of the apoenzymes due to the compound studied.