title: Rhodobacter sphaeroides uses a reductive route via propionyl coenzyme A to assimilate 3-hydroxypropionate.
abstract: 3-Hydroxypropionate is a product or intermediate of the carbon metabolism of organisms from all three domains of life. However, little is known about how carbon derived from 3-hydroxypropionate is assimilated by organisms that can utilize this C(3) compound as a carbon source. This work uses the model bacterium Rhodobacter sphaeroides to begin to elucidate how 3-hydroxypropionate can be incorporated into cell constituents. To this end, a quantitative assay for 3-hydroxypropionate was developed by using recombinant propionyl coenzyme A (propionyl-CoA) synthase from Chloroflexus aurantiacus. Using this assay, we demonstrate that R. sphaeroides can utilize 3-hydroxypropionate as the sole carbon source and energy source. We establish that acetyl-CoA is not the exclusive entry point for 3-hydroxypropionate into the central carbon metabolism and that the reductive conversion of 3-hydroxypropionate to propionyl-CoA is a necessary route for the assimilation of this molecule by R. sphaeroides. Our conclusion is based on the following findings: (i) crotonyl-CoA carboxylase/reductase, a key enzyme of the ethylmalonyl-CoA pathway for acetyl-CoA assimilation, was not essential for growth with 3-hydroxypropionate, as demonstrated by mutant analyses and enzyme activity measurements; (ii) the reductive conversion of 3-hydroxypropionate or acrylate to propionyl-CoA was detected in cell extracts of R. sphaeroides grown with 3-hydroxypropionate, and both activities were upregulated compared to the activities of succinate-grown cells; and (iii) the inactivation of acuI, encoding a candidate acrylyl-CoA reductase, resulted in a 3-hydroxypropionate-negative growth phenotype.
authors: Department of Microbiology, The Ohio State University, Columbus, Ohio, USA.
authors: Kathrin
authors: K
authors: Schneider
authors: Marie
authors: M
authors: Asao
authors: Michael S
authors: MS
authors: Carter
authors: Birgit E
authors: BE
authors: Alber
mesh_terms: D000214:Acyl Coenzyme A / Q000378:metabolism*; D044944:Acyl-CoA Dehydrogenases / Q000378:metabolism; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D004734:Energy Metabolism; D017353:Gene Deletion; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology; D019344:Lactic Acid / Q000031:analogs & derivatives* / Q000378:metabolism; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D012242:Rhodobacter sphaeroides / Q000378:metabolism*
chemical_list: D000214:Acyl Coenzyme A; D001426:Bacterial Proteins; C009061:propionyl-coenzyme A; D019344:Lactic Acid; C031601:hydracrylic acid; D044944:Acyl-CoA Dehydrogenases; C100154:acyl-CoA dehydrogenase (NADP+)