Enzymes metabolizing dimethylamine, trimethylamine and trimethylamine N ‐oxide in the yeast Sporopachydermia cereana grown on amines as sole nitrogen source

Sporopachydermia cereana , an ascosporogenous yeast, grew on dimethylamine, trimethylamine or trimethylamine N ‐oxide as sole nitrogen sources and produced mono‐oxygenases for dimethylamine and trimethylamine that were significantly more stable than the corresponding enzymes found in Candida utilis . No trimethylamine mono‐oxygenase activity was found in S. cereana grown on dimethylamine. In cells grown on trimethylamine N ‐oxide (but not on the other nitrogen sources), evidence for an enzyme metabolizing the N ‐oxide, possibly an aldolase, but more probably a reductase was obtained. All these activities showed a similar requirement for the presence of FAD or FMN in the extract buffer during isolation to retain activity. Amine mono‐oxygenase activities showed a similar sensitivity to inhibitors, including proadifen hydrochloride and carbon monoxide as the corresponding enzymes in C. utilis . The trimethylamine N ‐oxide‐dependent oxidation of NADH was more sensitive to inhibition by EDTA, N ‐ethylmaleimide and β‐phenylethylamine than the mono‐oxygenases, and less sensitive to KCN, and activity was significantly higher with NADPH than was observed with the 2 mono‐oxygenases.