title: Function of a glutathione-dependent formaldehyde dehydrogenase in Rhodobacter sphaeroides formaldehyde oxidation and assimilation.
abstract: Despite its reactivity with many biological molecules, formaldehyde can be commonly encountered by virtually all cells. The widespread existence of glutathione-dependent formaldehyde dehydrogenases (GSH-FDH) in procaryotes and eucaryotes suggests this enzyme plays a central and universal role in biological formaldehyde oxidation. This work sought to determine the role of GSH-FDH in the facultative phototrophic bacterium Rhodobacter sphaeroides. Growth phenotypes of wild-type and mutant cells, changes in enzyme specific activities, and the pattern of 13C-labeled compounds detected by NMR spectroscopy cumulatively suggest that R. sphaeroides GSH-FDH can play a critical role in formaldehyde metabolism under both photosynthetic and aerobic respiratory conditions. In photosynthetic cells, the data indicate that GSH-FDH generates reducing power, in the form of NADH, and one-carbon skeletons that are oxidized to carbon dioxide for subsequent assimilation by the Calvin-Benson-Bassham cycle. For example, use of methanol as a sole photosynthetic carbon source increases the specific activities of GSH-FDH, an NAD-dependent formate dehydrogenase, and the key Calvin-Benson-Bassham cycle enzyme, ribulose-1,5-bisphosphate carboxylase. This role of GSH-FDH is also supported by the pattern of [13C]formaldehyde oxidation products that accumulate in photosynthetic cells and the inability of defined GSH-FDH or Calvin cycle mutants to use methanol as a sole carbon source. Our data also suggest that GSH-FDH acts in formaldehyde dissimilation when aerobic respiratory cultures cometabolize methanol and succinate.
authors.affiliation: Graduate Program in Cell and Molecular Biology and Department of Bacteriology, University of Wisconsin--Madison, Madison, Wisconsin 53706, USA.
authors.forename: R D
authors.initials: RD
authors.lastname: Barber
authors.forename: T J
authors.initials: TJ
authors.lastname: Donohue
mesh_terms: D000332:Aerobiosis; D000445:Aldehyde Oxidoreductases / Q000378:metabolism*; D002245:Carbon Dioxide / Q000378:metabolism; D003574:Cytochrome c Group / Q000378:metabolism; D045304:Cytochromes c; D005557:Formaldehyde / Q000378:metabolism*; D008954:Models, Biological; D010084:Oxidation-Reduction; D010101:Oxygen Consumption; D010788:Photosynthesis; D012242:Rhodobacter sphaeroides / Q000201:enzymology*; D012273:Ribulose-Bisphosphate Carboxylase / Q000378:metabolism
chemical_list: D003574:Cytochrome c Group; C032139:iso-2-cytochrome C; D002245:Carbon Dioxide; D005557:Formaldehyde; D045304:Cytochromes c; C020145:formaldehyde dehydrogenase (glutathione); D000445:Aldehyde Oxidoreductases; D012273:Ribulose-Bisphosphate Carboxylase