Inhibition of aminoacid decarboxylases by non-steroidal antiinflammatory drugs.

Several non-steroidal antiinflammatory drugs (NSAID) were shown to inhibit to various extents the decarboxylases of ornithine, lysine, histidine, arginine, and tyrosine. The most sensitive enzyme was ornithine decarboxylase, for which piroxicam, benoxaprofen and aminophenazone showed an IC50 of 0.007 mM; ibuprofen competitively inhibits the lysine decarboxylase. The most effective NSAID's in inhibiting histidine decarboxylase were mefenamic acid, ibuprofen and flufenamic acid. Arginine and tyrosine decarboxylase were inhibited by NSAID's only at high concentrations. None of the decarboxylase inhibitions were reversed by pyridoxal phosphate. Subplantar injection of the 5 amines formed by these aminoacid decarboxylases elicited a paw oedema in rat which was not antagonized by the various NSAID's. Some of the NSAID's stimulated all the decarboxylases and did not antagonize the carrageenin-induced paw oedema. With one exception, all the NSAID's tested in vivo inhibited the elimination of 14CO2 from labeled ornithine and lysine. The inhibition of certain aminoacid decarboxylases, particularly ornithine and lysine decarboxylase, appears to be a noteworthy mechanism of action for certain NSAID's.