ISOLATION, SEQUENCING, AND MUTAGENESIS OF THE GENE ENCODING NAD-DEPENDENT AND GLUTATHIONE-DEPENDENT FORMALDEHYDE DEHYDROGENASE (GD-FALDH) FROM PARACOCCUS-DENITRIFICANS, IN WHICH GD-FALDH IS ESSENTIAL FOR METHYLOTROPHIC GROWTH

NAD- and glutathione-dependent formaldehyde dehydrogenase (GD-FALDH) of Paracoccus denitrificans;ans has been purified as a tetramer with a relative molecular mass of 150 kDa. The gene encoding GD-FALDH (flhA) has been isolated, sequenced, and mutated by insertion of a kanamycin resistance gene. The mutant strain is not able to grow on methanol, methylamine, or choline, while heterotrophic growth is not influenced by the mutation. This finding indicates that GD-FALDH of P. denitrificans is essential for the oxidation of formaldehyde produced during methylotrophic growth.