FORMALDEHYDE DISMUTASE ACTIVITIES IN GRAM-POSITIVE BACTERIA OXIDIZING METHANOL

Extracts of methanol-grown cells of Amycolatopsis methanolica and Mycobacterium gastri oxidized methanol and ethanol with concomitant reduction of N,N'-dimethyl-4-nitrosoaniline (NDMA). Anion-exchange chromatography revealed the presence of a single enzyme able to catalyse this activity in methanol- or ethanol-grown cells of M. gastri. A. methanolica, however, possessed two different enzymes, one of which was similar to the single enzyme found in M. gastri. The methanol: NDMA oxidoreductases (MNO) were purified to homogeneity from methanol-grown cells of A. methanolica and M. gastri. Both enzyme preparations showed similar relative molecular masses with subunits of M(r) 50 000 and 49 000, and native enzymes of M(r) 268 000 and 255 000 (gel-filtration data for A. methanolica and M. gastri, respectively). Both enzymes also displayed a similar substrate specificity. They were active with methanol and various other primary alcohols (yielding the corresponding aldehydes), polyols and formaldehyde. In addition, the MNO enzymes produced methylformate from methanol plus formaldehyde, and catalyzed formaldehyde dismutase and NADH-dependent formaldehyde reductase reactions. They did not possess NAD(P)+- or dye-linked alcohol dehydrogenase or oxidase activities.