A study of the overcoming the weak point of a nutritional supplementary food, Spirulina in nutrition

螺旋藻(Spirulina sp.，一种蓝藻)是一种营养补充性食品，含有大量对人体无活性的7-腺苷酰可巴胺(7-Adenyl Cobamde，伪维生素B；12&gt；)。假维生素B_(12)的生理功能钝顶螺旋藻含有大量的假维生素B_(12)和高比活性的依赖于维生素B_(12)的蛋氨酸合成酶。对钝顶螺旋藻依赖维生素B的蛋氨酸合成酶基因进行了分子克隆。从细胞中提取螺旋藻基因组DNA。简并引物是从已知的其他蓝藻冰毒的保守序列中指定的。利用所设计的引物对纯化的DNA进行聚合酶链式反应(PCR)。开放阅读框为3549个碱基。推导出的氨基酸序列与红曲霉EMS 101甲基有很高的相似性。维生素B_(12)和S-腺苷-L-蛋氨酸的结合基序完全保守。这些结果表明，开放阅读框编码一种冰毒。结论：1.假维生素B_12&gt；可能是钝顶螺旋体蛋氨酸合成酶的辅酶。当5，6-二甲基苯并咪唑作为维生素B_12的低核苷酸部分的前体加入到培养液中时，加入B_(12)前体的影响，以评价假维生素B_(12)在细菌细胞中是否转化为真正的维生素B_(12)。前体的加入显著抑制了细胞的生长。

A nutritional supplementary food, Spirulina (Spirulina sp., a cyanobacterium), contains substantial amount of 7-adenynyl cobaminde (pseudovitamin B_<12>), which is inactive for humans.To overcome the weak point of the Spirulina food in nutrition, fundamental information on physiological function and biosynthesis of pseudovitamin B_<12> in the bacterial cells was studied.1. Physiological function of pseudovitamin B_<12>Spirulina platensis contains substantial amount of pseudovitamin B_<12> and high specific activity of vitamin B_<12>-dependent methionine synthase. Molecular cloning of the vitamin B_<12>-dependent methionine synthase gene form S. platensis was conducted. Spirulina genomic DNA was purified from the cell. The degenerate primers were designated from well-conserved sequences of the known other cyanobacterial MetH. Using the primers, purified DNA was amplified by PCR. An open reading frame is 3549bp. The deduced amino add sequence showed high similarity to Thichodesmium erythraeum EMS 101 MetH. The binding motif of vitamin B_<12> and s-adenosyl-L-methioneni are completely conserved. These results indicated that the open reading frame encodes a metH. Pseudovitamin B_<12> may function as the coenzyme of the methionine synthase in S. platensis.2. Effect of the addition of precursor of B_<12>When 5,6-dimethylbenzimidazol as a precursor of the lower nucleotide moiety of vitamin B_<12> was added to the medium in order to evaluate whether pseudovitamin B_<12> is converted to true vitamin B_<12> in the bacterial cells. The addition of the precursor inhibited significant the cell growth.