title: Occurrence of pseudovitamin B12 and its possible function as the cofactor of cobalamin-dependent methionine synthase in a cyanobacterium Synechocystis sp. PCC6803.
abstract: To clarify the physiological function of pseudovitamin B(12) in cyanobacteria, we determined pseudovitamin B(12) contents and cobalamin-dependent methionine synthase activity in Synechocystis sp. PCC6803 grown under CoSO(4)-sufficient and -limited conditions. Pseudovitamin B(12) and cobalamin-dependent methionine synthase activity (0.8 nmol/min/mg protein) were found in a homogenate of the Synechocystis cells grown for 10 d in the CoSO(4)-sufficient medium. The cellular pseudovitamin B(12 )contents increased significantly at the early logarithmic growth phase and thereafter decreased rapidly at the stationary phase; a similar fluctuation pattern was shown in the cobalamin-dependent methionine synthase activity. Although the CoSO(4)-limited conditions did not reduce the cell growth, pseudovitamin B(12) contents and methionine synthase activity decreased significantly in the limited cells relative to the sufficient cells. These results indicate that the cyanobacterium Synechocystis sp. PCC6803 can synthesize pseudovitamin B(12) de novo and utilize it as the cofactor for cobalamin-dependent methionine synthase.
authors.affiliation: Department of Nutrition, Junior College of Tokyo University of Agriculture, Setagaya-ku, Tokyo, Japan. y3taniok@nodai.ac.jp
authors.forename: Yuri
authors.initials: Y
authors.lastname: Tanioka
authors.forename: Yukinori
authors.initials: Y
authors.lastname: Yabuta
authors.forename: Ryoichi
authors.initials: R
authors.lastname: Yamaji
authors.forename: Shigeru
authors.initials: S
authors.lastname: Shigeoka
authors.forename: Yoshihisa
authors.initials: Y
authors.lastname: Nakano
authors.forename: Fumio
authors.initials: F
authors.lastname: Watanabe
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Inui
mesh_terms: D013766:5-Methyltetrahydrofolate-Homocysteine S-Methyltransferase / Q000378:metabolism*; D018929:Cell Culture Techniques; D049109:Cell Proliferation; D003067:Coenzymes / Q000032:analysis* / Q000096:biosynthesis; D046939:Synechocystis / Q000737:chemistry / Q000254:growth & development / Q000378:metabolism*; D014805:Vitamin B 12 / Q000031:analogs & derivatives* / Q000032:analysis / Q000096:biosynthesis / Q000378:metabolism*; D014806:Vitamin B 12 Deficiency / Q000378:metabolism*
chemical_list: D003067:Coenzymes; C005602:pseudovitamin B12; D013766:5-Methyltetrahydrofolate-Homocysteine S-Methyltransferase; D014805:Vitamin B 12