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标题：Precursor of Carbon Atom Five and Hydroxymethyl Carbon Atom of the Pyrimidine Moiety of Thiamin in Escherichia coil
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作者：Kazuko YAMADA ; Hiroshi KUMAOKA
期刊名称：Journal of Nutritional Science and Vitaminology
印刷版ISSN：0301-4800
电子版ISSN：1881-7742
出版年度：1983
卷号：29
期号：4
页码：389-398
DOI：10.3177/jnsv.29.389
出版社：Center for Academic Publications Japan
摘要：The pyrimidine moiety of thiamin can be synthesized in bacteria from 5-aminoimidazole ribotide (AIR), an intermediate in purine biosynthesis. To transform the imidazole ring of AIR to the pyrimidine, the bond between C-4 and C-5 of the imidazole ring should be ruptured and a two-carbon unit should be inserted. We investigated a precursor of the two-carbon unit which should be inserted to form the pyrimidine. To examine the possibility of the twocarbon compound as a precursor which is formed from a three-carbon intermediate in the glycolytic pathway and its three-carbon derivative by decarboxylation in cells, we studied the incorporation of [2-¹⁴C]glycerol, [2-¹⁴C]pyruvate, [U-¹⁴C]alanine and [3-¹⁴C]serine into the pyrimidine by Escherichia coli. Glycerol, pyruvate and alanine were not incorporated into the pyrimidine. Radioactive carbon of [3-¹⁴C]serine was incorporated into C-2 of the pyrimidine via one-carbon units pool. Then, we investigated the possibility of a ribose moiety of AIR being a precursor of the two-carbon unit. As ribose has low permeability into E. coli cells, the ribose moiety of AIR was labeled with [¹⁴C]glucose which was added to the growth medium. The results show that two radioactive carbons of [U-¹⁴C]glucose were incorporated into the pyrimidine and radioactive carbon of [6-¹⁴C]glucose was incorporated into hydroxymethyl carbon attached to C-5 of the pyrimidine. The dilution rates of the specific radioactivity of the pyrimidine from [U-¹⁴C]glucose and [6-¹⁴C]glucose well coincide with those of the ribose moiety of the nucleotide (AMP). Radioactive carbon of [1-¹⁴C]glucose was not incorporated into the pyrimidine and nucleotide. It is concluded that the two-carbon fragment derived from C-4' and C-5' of the ribose moiety of AIR can be incorporated into the pyrimidine moiety of thiamin as the precursor of C-5 and hydroxymethyl carbon.
关键词：biosynthesis of thiamin;pyrimidine moiety of thiamin;5-aminoimidazole ribotide;Escherichia coli