EFFECT OF SOME STEROIDAL AND NONSTEROIDAL ANTIINFLAMMATORY DRUGS ON PURIFIED GOAT BRAIN CATHEPSIN-L

The lysosomal cysteine proteinases have been found to be involved in v arious inflammatory conditions. Inhibitory effects of certain commonly used anti-inflammatory drugs were observed on lysosomal thiol protein ase cathepsin L. Of the non-steroidal anti-inflammatory drugs tested, phenylbutazone was found to be most potent inhibitor of cathepsin L ac tivity. The half maximal inhibition was achieved at 0.6 mM concentrati on. The inhibition by phenylbutazone was of non-competitive type, with a k(i) of 1.3 x 10(-3) M. Flufenamic acid and indomethacin were also inhibitory to cathepsin L activity, giving half maximal inhibitions at 3.5 mM and 4.5 mM concentrations respectively. In contrast, cathepsin L activity was not affected at all by steroidal anti-inflammatory age nts. Aspirin was also found to have no effect on cathepsin L activity whereas salicylic acid, its m- and p-analogs exhibited inhibitory effe cts but to a lesser degree.