PATHWAYS OF GLUTAMATE CATABOLISM AMONG FUSOBACTERIUM SPECIES
PATHWAYS OF GLUTAMATE CATABOLISM AMONG FUSOBACTERIUM SPECIES
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DOI：
10.1099/00221287-137-5-1201
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发表时间：
1991-05-01
期刊：
影响因子：
--
通讯作者：
SHAH, HN
中科院分区：
文献类型：
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作者：
GHARBIA, SE;SHAH, HN
谷氨酸是梭杆菌的主要能量来源，但其分解代谢模式迄今尚未阐明。分别来自口腔和胃肠道的具代表性的核仁F. （F. nucleatum）和变异F. （F. varium）的细胞悬液都脱除了位置标记谷氨酸，但途径不同。14 . F. nucleatum仅从C-5释放co2，而F. varium则在C-1或C-5脱羧谷氨酸。在这两个物种中，2 mol的谷氨酸发酵产生2 mol的乙酸和1 mol的丁酸，表明可能有3种代谢途径：2-氧戊二酸途径、mesaconate途径和4-氨基丁酸途径。在梭杆菌的无细胞提取物中测定了代表这三种途径的酶。所有被测物种均具有高水平的谷氨酸脱氢酶和2-氧戊二酸还原酶，表明2-氧戊二酸途径的存在。在F. sulci、F. ulcerans、F. mortiferum和F. varium中检测到具有mesaconate途径代表的酶，而后两个物种也具有4-氨基丁酸途径。因此，谷氨酸分解代谢的途径与所测试的梭杆菌的分离位点无关，而是与它们的化学分类特性相关。因此，F. varium， F. mortiferum， F. ulcerans和F. sulci具有基于二氨基戊酸的肽聚糖结构，具有两种或三种谷氨酸分解代谢途径，而F. nucleatum和其他具有基于硫代蛋白的鼠蛋白的物种仅通过2-氧葡萄糖酸途径代谢谷氨酸。
Glutamate is a major source of energy for Fusobacterium species but its mode of catabolism has not hitherto been elucidated. Cell suspensions of F. nucleatum and F. varium, as representative species from the oral cavity and gastrointestinal tract, respectively, both decarboxylated position-labelled glutamate but by different pathways. 14CO2 was released only from C-5 by F. nucleatum whereas F. varium decarboxylated glutamate at either C-1 or C-5. In both species, 2 mols of glutamate fermented yielded 2 mols of acetate and 1 mol of butyrate, suggesting the possibility of three metabolic pathways: the 2-oxoglutarate, mesaconate and 4-aminobutyrate pathways. Enzymes representative of the three pathways were assayed for in cell-free extracts of fusobacteria. All species tested possessed high levels of both glutamate dehydrogenase and 2-oxoglutarate reductase, indicating the presence of the 2-oxoglutarate pathway. Enzymes representative of the mesaconate pathway were detected in F. sulci, F. ulcerans, F. mortiferum and F. varium, while the latter two species also possessed the 4-aminobutyrate pathway. The pathways of glutamate catabolism therefore bore no relationship to the site of isolation of the fusobacteria tested but instead correlated with their chemotaxonomic properties. Thus, F. varium, F. mortiferum, F. ulcerans and F. sulci, which possess a peptidoglycan structure based on diaminopimelic acid, have either two or three pathways for glutamate catabolism whereas F. nucleatum and other species that have a lanthionine-based murein metabolized glutamate solely by the 2-oxoglutarate pathway.