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

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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.