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.
从自然界中分离出利用甘露醇酸作为能源的细菌。其中一种被鉴定为属于嗜水气单胞菌属的生物,能够将葡萄糖醛酸、半乳糖醛酸和甘露醛酸作为唯一的碳和能源来源。葡萄糖醛酸和半乳糖醛酸生长的休眠细胞能迅速氧化这两种醛酸,但是甘露醛酸的氧化速度较慢。生长在甘露醛酸上的细胞能迅速氧化这三种醛酸,但甘露醛酸的利用速率略低。从葡萄糖醛酸、半乳糖醛酸和甘露醛酸生长的嗜水气单胞菌C11-2B中提取的无细胞酶液含有葡萄糖醛酸和半乳糖醛酸异构酶、果糖醛酸、他加醛酸和甘露醛酸还原酶,以及甘醇酸和阿尔醇酸脱水酶,但葡萄糖醛酸生长的细胞缺乏阿尔醇酸脱水酶。因此,嗜水气单胞菌的葡萄糖醛酸和半乳糖醛酸分解途径与大肠杆菌相同。葡萄糖醛酸和半乳糖醛酸被异构化为D-果糖醛酸和D-他加醛酸,然后被还原型烟酰胺腺嘌呤二核苷酸还原为D-甘露醛酸和D-阿尔醇酸。这些己糖酸被脱水为2-酮-3-脱氧葡萄糖酸,然后被三磷酸腺苷磷酸化为2-酮-3-脱氧-6-磷酸葡萄糖酸。后者随后被分解为丙酮酸和甘油醛-3-磷酸。甘露醛酸被还原为D-甘露醛酸,由还原型烟酰胺腺嘌呤二核苷酸磷酸化。D-甘露醛酸随后像葡萄糖醛酸途径一样被进一步分解。该酶是首个将醛基六元糖酸还原为己糖酸的细菌氧化还原酶。该酶应该证明是一种有用的分析工具,用于在存在其他羧酸的情况下测定甘露醛酸。