ISOTHIAZOLONE BIOCIDES - ENZYME-INHIBITING PRO-DRUGS

Previous investigations indicate that there are basic differences in the antimicrobial activity of the chlorinated and non-chlorinated isothiazolones. These differences appear to result from the formation of a highly reactive thio-acyl chloride tautomer by the chlorinated isothiazolones. In the present investigations the effects of the isothiazolones upon the activity of yeast alcohol dehydrogenase are examined in the presence and absence of various potential neutralisers of their activity. Results indicate that thiol containing compounds may both neutralise and, at lower concentrations, potentiate the inhibitory activity of 5-chloro-N-methylisothiazolone. Such potentiation was not observed when the experiments were repeated with benzisothiazolone. The presence of thiol at concentrations which potentiate antimicrobial action enhanced the inhibitory activity of 5-chloro-N-methylisothiazolone towards alcohol dehydrogenase when ethanol-limited. This was not observed with benzisothiazolone challenged enzyme.