Conversion of 5-aminoimidazole ribotide to the pyrimidine of thiamin in enterobacteria: study of the pathway with specifically labeled samples of riboside.
Samples of 5-amino-1-(beta-D-ribofuranosyl)imidazole labeled with 13C at position C-1 or C-2 of the ribose part or with 15N at position N-3 or amino of the imidazole part were prepared by chemical synthesis. The incorporation of label from these samples into the pyrimidine of thiamin biosynthesized by a mutant strain of Salmonella typhimurium was studied by GC-MS. The results show clearly that in enterobacteria the methyl carbon atom and the N-1 nitrogen atom of one molecule of thiamin pyrimidine derive from the same molecule of 5-aminoimidazole ribotide. More specifically, the methyl carbon atom comes from the carbon C-2' of the ribose part and the nitrogen N-1 from nitrogen N-3 of the imidazole; furthermore, the amino nitrogen of the aminoimidazole becomes the amino nitrogen of the pyrimidine.
Institut de Chimie Moléculaire d'Orsay, Laboratoire de Chimie Organique Multifonctionelle associé au CNRS, URA 462, Université de Paris-Sud, France.
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Estramareix
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David
D002247:Carbon Isotopes; D008401:Gas Chromatography-Mass Spectrometry; D007202:Indicators and Reagents; D009154:Mutation; D012265:Ribonucleotides / Q000138:chemical synthesis / Q000378:metabolism*; D012486:Salmonella typhimurium / Q000235:genetics / Q000378:metabolism*; D013831:Thiamine / Q000096:biosynthesis*
D002247:Carbon Isotopes; D007202:Indicators and Reagents; D012265:Ribonucleotides; C024828:aminoimidazole ribotide; D013831:Thiamine