title: Aldohexuronic acid catabolism by a soil Aeromonas.
abstract: Bacteria which utilize mannuronic acid as an energy source were isolated from nature. One of the organisms, identified as a member of the genus Aeromonas, used glucuronate, galacturonate, and mannuronate as the sole source of carbon and energy. Glucuronate- and galacturonate-grown resting cells oxidized both glucuronate and galacturonate rapidly, but mannuronate slowly. Mannuronate-grown cells oxidized all three rapidly, with the rate of mannuronate utilization somewhat lower. Cell-free extracts from glucuronate-, galacturonate-, and mannuronate-grown Aeromonas C11-2B contained glucuronate and galacturonate isomerases, fructuronate, tagaturonate, and mannuronate reductases, and mannonate and altronate dehydratases, with the exception of glucuronate-grown cells which lacked altronate dehydratase. Thus, the pathway for glucuronate and galacturonate catabolism for Aeromonas was identical to Escherichia coli. Glucuronate and galacturonate were isomerized to d-fructuronate and d-tagaturonate which were then reduced by reduced nicotinamide adenine dinucleotide to d-mannonate and d-altronate, respectively. The hexonic acids were dehydrated to 2-keto-3-deoxy gluconate which was phosphorylated by adenosine triphosphate to 2-keto-3-deoxy-6-phospho gluconate. The latter was then cleaved to pyruvate and glyceraldehyde-3-phosphate. Mannuronate was reduced directly to d-mannonate by a reduced nicotinamide adenine dinucleotide phosphate-linked oxidoreductase. d-Mannonate was then further broken down as in the glucuronate pathway. The mannuronate reducing enzyme, for which the name d-mannonate:nicotinamide adenine dinucleotide (phosphate) oxidoreductase (d-mannuronate-forming) was proposed, was shown to be distinct from altronate and mannoate oxidoreductases. This is the first report of a bacterial oxidoreductase which reduces an aldohexuronic acid to a hexonic acid. The enzyme should prove to be a useful analytical tool for determining mannuronate in the presence of other uronic acids.
mesh_terms: D000333:Aeromonas / Q000378:metabolism*; D000429:Alcohol Oxidoreductases / Q000378:metabolism; D005632:Fructose; D005690:Galactose / Q000378:metabolism; D005965:Glucuronates; D005985:Glyceraldehyde / Q000096:biosynthesis; D006836:Hydro-Lyases / Q000378:metabolism; D007535:Isomerases / Q000378:metabolism; D008358:Mannose / Q000378:metabolism; D009249:NADP; D010088:Oxidoreductases / Q000378:metabolism*; D010710:Phosphates / Q000096:biosynthesis; D011773:Pyruvates / Q000096:biosynthesis; D012988:Soil Microbiology; D009626:Terminology as Topic; D014574:Uronic Acids / Q000378:metabolism*
chemical_list: D005965:Glucuronates; D010710:Phosphates; D011773:Pyruvates; D014574:Uronic Acids; D005632:Fructose; D005985:Glyceraldehyde; D009249:NADP; D010088:Oxidoreductases; D000429:Alcohol Oxidoreductases; D006836:Hydro-Lyases; D007535:Isomerases; D008358:Mannose; D005690:Galactose