Inhibition of aromatic amino acid decarboxylases by the anti-inflammatory agent flobufen and 2',4'-difluorbiphenyl-4-acetic acid

The effect of the novel Czechoslovak antiphlogistic agent flobufen (VUFB 16066, 4-[2',4'-difluorbiphenyl]-4-oxo-methyl-butanic acid) and its metabolite 2',4'-difluorbiphenyl-4-yl acetic acid (VUFB 17203) on decarboxylase of aromatic amino acids (DAAK, E. C. 4.1.1.28) of the rat liver (supernatant 20,000 x g) was studied in vitro. The concentrations of 3.8 x 10(-4) mol x 1(-1) of flobufen and 4.4 x 10(-4) mol x 1(-1) of difluorbiphenylyl acetic acid produced 50% inhibition n the enzyme. Ki for flobufen is approximately 1.5 x 10(-4) mol x 1(-1), the reaction with the inhibitor takes place in the ratio 1:1 and the enzyme-inhibitor complex does not exert any catalytic activity. In the tissues with a low activity of DAAK, inhibition could be manifested by decreased synthesis of serotonin and dopamine.