Goff R C, Hartman R E
J Bacteriol. 1970 Oct;104(1):27-33. doi: 10.1128/jb.104.1.27-33.1970.
Fixation of NaH(14)CO(3) by a heavy cell suspension of Streptococcus faecalis var. liquefaciens was studied. Several nutrients, pyridoxal, riboflavine, adenine, uracil, and O(2) stimulated (14)CO(2) incorporation into cells only under conditions that were adequate for synthesis of cell macromolecules. Biotin increased CO(2) incorporation in the absence of extensive synthesis of macromolecules, whereas O(2) inhibited incorporation under these conditions. When (14)CO(2) fixation was occurring during synthesis of macromolecules, 71% of the (14)C was incorporated into cells and 29% occurred extracellularly. Ninety-three per cent of the cellular (14)C was in protein and 5.5% was in nucleic acid. Aspartic acid was the only amino acid in the protein fraction that was radioactive. Eighty-three per cent of the extracellular (14)C was resistant to precipitation by trichloroacetic acid. When (14)CO(2) fixation was occurring in cells that were not carrying on extensive synthesis of macromolecules, 38% of the (14)C was incorporated into cells and 59% occurred in the supernatant fluid. Sixty-nine per cent of the cellular (14)C was in protein, 21% was in low-molecular-weight compounds, and 9% was in nucleic acid. Addition of unlabeled aspartate to the medium inhibited incorporation of (14)CO(2). Based on studies of the rate of (14)CO(2) fixation, the cells fix CO(2) into a pool of intermediates which are either used for synthesis, primarily protein, or are excreted into the medium.
研究了液化粪链球菌重细胞悬液对NaH(14)CO(3)的固定作用。几种营养物质,如吡哆醛、核黄素、腺嘌呤、尿嘧啶和O(2),仅在足以合成细胞大分子的条件下才刺激(14)CO(2)掺入细胞。生物素在没有广泛合成大分子的情况下增加了CO(2)的掺入,而在这些条件下O(2)抑制了掺入。当在大分子合成过程中发生(14)CO(2)固定时,71%的(14)C掺入细胞,29%存在于细胞外。细胞中93%的(14)C存在于蛋白质中,5.5%存在于核酸中。天冬氨酸是蛋白质部分中唯一具有放射性的氨基酸。细胞外83%的(14)C对三氯乙酸沉淀有抗性。当在没有进行广泛大分子合成的细胞中发生(14)CO(2)固定时,38%的(14)C掺入细胞,59%存在于上清液中。细胞中69%的(14)C存在于蛋白质中,21%存在于低分子量化合物中,9%存在于核酸中。向培养基中添加未标记的天冬氨酸会抑制(14)CO(2)的掺入。基于对(14)CO(2)固定速率的研究,细胞将CO(2)固定到一个中间产物池中,这些中间产物要么用于合成,主要是蛋白质,要么排泄到培养基中。