title: Biosynthesis of thiamine: origin of the methyl carbon atom of the pyrimidine moiety in Salmonella typhimurium.
abstract: Two biosynthetic, unevenly labeled samples of 5-aminoimidazole riboside were prepared. The incorporation of radioactivity from these labeled samples was studied in a Salmonella typhimurium strain able to use this riboside as precursor of the pyrimidine moiety of thiamine. In one sample, the ribose part was labeled almost equally at C-1' and C-2' and threefold more at C-3' but unlabeled at C-4' and C-5'. The pyrimidine moiety of thiamine derived from it was found almost inactive at C-5, C-7; the specific activity of the methyl carbon atom was found close to that of C-1' or C-2' of ribose in the precursor. On the other hand, only a poor incorporation of radioactivity occurred from a sample in which the ribose part was labeled mainly at C-1'. We conclude that C-5, C-7 of the pyrimidine moiety of thiamine derive from C-4', C-5' and the methyl carbon atom of the pyrimidine derives from C-2' of the ribose part of 5-aminoimidazole ribotide.
authors.forename: B
authors.initials: B
authors.lastname: Estramareix
authors.forename: S
authors.initials: S
authors.lastname: David
mesh_terms: D001665:Binding Sites; D055598:Chemical Phenomena; D002621:Chemistry; D008745:Methylation; D011743:Pyrimidines / Q000032:analysis; D012265:Ribonucleotides / Q000378:metabolism; D012266:Ribose / Q000032:analysis; D012486:Salmonella typhimurium / Q000378:metabolism*; D013831:Thiamine / Q000096:biosynthesis*
chemical_list: D011743:Pyrimidines; D012265:Ribonucleotides; C024828:aminoimidazole ribotide; D012266:Ribose; C030986:pyrimidine; D013831:Thiamine