Robertson D E, Roberts M F, Belay N, Stetter K O, Boone D R
Department of Chemistry, Boston College, Chestnut Hill, Massachusetts 02167.
Appl Environ Microbiol. 1990 May;56(5):1504-8. doi: 10.1128/aem.56.5.1504-1508.1990.
The unusual compound beta-aminoglutaric acid (beta-glutamate) has been identified by 13C nuclear magnetic resonance spectroscopy in soluble extracts of marine methanogenic bacteria. We examined several methanogen species representing nine genera and found that beta-glutamate occurred in methanococci and two methanogenium strains (Methanogenium cariaci JR1 and "Methanogenium anulus" AN9). The presence of this compound in the methanococci examined was further restricted to thermophilic members of the genus Methanococcus, including Methanococcus thermolithotrophicus strains, Methanococcus jannaschii, and "Methanococcus igneus." The two Methanogenium strains examined were mesophiles. Studies using Methanococcus thermolithotrophicus showed that levels of beta-glutamate in cells of that species were not affected by variation in growth temperature (40 to 65 degrees C), NH4+ (2 to 80 mM), Mg2+ (10 to 50 mM), or K+ (2 to 10 mM) in the medium. In contrast, soluble pools of beta-glutamate and L-alpha-glutamate (the other major free amino acid in all the methanococci) were proportional to NaCl levels in the growth medium. This dependence of beta-glutamate and L-alpha-glutamate concentrations on salt levels in the medium suggests that they function as osmolytes in these cells.
已通过13C核磁共振光谱法在海洋产甲烷菌的可溶性提取物中鉴定出异常化合物β-氨基戊二酸（β-谷氨酸）。我们检测了代表9个属的几种产甲烷菌，发现β-谷氨酸存在于甲烷球菌和两株产甲烷菌（卡里亚产甲烷菌JR1和“环形产甲烷菌”AN9）中。在所检测的甲烷球菌中，该化合物的存在进一步局限于嗜热的甲烷球菌属成员，包括嗜热自养甲烷球菌菌株、詹氏甲烷球菌和“火栖甲烷球菌”。所检测的两株产甲烷菌是嗜温菌。对嗜热自养甲烷球菌的研究表明，该菌种细胞中β-谷氨酸的水平不受培养基中生长温度（40至65摄氏度）、NH4+（2至80 mM）、Mg2+（10至50 mM）或K+（2至10 mM）变化的影响。相比之下，β-谷氨酸和L-α-谷氨酸（所有甲烷球菌中的另一种主要游离氨基酸）的可溶性池与生长培养基中的NaCl水平成正比。β-谷氨酸和L-α-谷氨酸浓度对培养基中盐水平的这种依赖性表明它们在这些细胞中起渗透调节剂的作用。
