S-Oxygenation of an alkylmercaptotriazine herbicide by rat, rabbit and human liver enzymes

Abstract

1. The oxidation of the herbicide cyanatryn to cyanatryn S-oxide and de-ethylcyanatryn was used to study S-oxidation and N-de-ethylation in liver microsomes from three species.

2. Both reactions were dependent upon NADPH and were inhibited by metyrapone and CO. However, the enzyme catalysing N-de-ethylation exhibited different species/sex specificity from the S-oxygenase.

3. Rat liver flavoprotein S-oxygenase had no action on cyanatryn, suggesting, with the other data, that the S-oxygenation was catalysed by cytochrome P-450.

4. S-Oxygenation proceeded rapidly in human liver microsomes and the rate was linear for 60 min at 37°C.