NAD-SUBSTRATE AND COSUBSTRATE (GSH OR FACTOR)-DEPENDENT FORMALDEHYDE DEHYDROGENASES FROM METHYLOTROPHIC MICROORGANISMS ACT AS A CLASS-III ALCOHOL-DEHYDROGENASE

The methylotrophic yeasts, Hansenula polymorpha and Candida boidinii, and the methylotrophic Gram-negative bacteria, Paracoccus denitrificans and Thiobacillus versutus (but not Methylophaga marina), contain NAD/GSH-dependent formaldehyde dehydrogenase when grown on C-1-compounds. The enzymes appeared to be similar to each other and to the mammalian counterparts with respect to substrate specificity, including the ability to act as an alcohol dehydrogenase class III. The Gram-positive bacteria, Amycolatopsis methanolica and Rhodococcus erythropolis, possess NAD/Factor-dependent formaldehyde dehydrogenase when grown on C-1-compounds or on C-1-unit-containing substrates, respectively. These enzymes also exhibit alcohol dehydrogenase class III activity. Thus, like the mammalian ones, methylotrophic formaldehyde dehydrogenases show dual substrate specificity, suggesting that this is an inherent property of the enzyme.