Biosynthesis of the pyrimidine moiety of thiamine. A new route of pyrimidine biosynthesis involving purine intermediates

Abstract

1. The pattern of distribution on the purine pathway of mutants of Salmonella typhimurium LT2 that had the double growth requirement for a purine plus the pyrimidine moiety of thiamine (ath mutants) indicated that purines and the pyrimidine moiety of thiamine share the early part of their biosynthetic pathways, and that 4-aminoimidazole ribonucleotide (AIR) is the last common intermediate. Two mutants that at first appeared anomalous were further investigated and found not to affect this deduction. 2. The ribonucleoside form of AIR (AIR(s)) satisfied the requirements both for a purine and for the pyrimidine moiety of thiamine of an ath mutant. 3. Methionine was required for the conversion of AIR into the pyrimidine moiety. 4. Radioactive AIR(s) was converted into radioactive pyrimidine moiety by an ath mutant without significant dilution of specific radioactivity. 5. Possible mechanisms for pyrimidine-moiety biosynthesis from AIR are discussed.

A Genetic Screen for the Identification of Thiamin Metabolic Genes

“…1) (1-5). 5-Aminoimidazole ribonucleotide serves as the precursor to 4-amino-2-methyl-5-hydroxymethylpyrimidine phosphate (HMP-P) (6), and 4-methyl-5-(␤-hydroxyethyl)thiazole phosphate is formed in a complex condensation from 1-deoxy-D-xylulose-5-phosphate, glycine, and cysteine (7). A phosphorylation catalyzed by ThiL provides the active cofactor TPP.…”

Precursor of carbon atom five and hydroxymethyl carbon atom of the pyrimidine moiety of thiamin in Escherichia coli.

“…Newell and Tucker (1) proposed that in Salmonella typhimurium, the pyrim idine moiety of thiamin is synthesized from AIR, an intermediate in purine bio synthesis. The transformation of the imidazole ring of AIR into the pyrimidine should be accomplished by ring expansion reaction.…”

Overproduction of Hydroxymethylpyrimidine by a Thiamine Regulatory Mutant of Escherichia coli

“…In this paper we report that this precursor accumulated was identified as hydroxymethyl pyrimidine, and the mechanism of accumula tion of hydroxymethylpyrimidine and some conditions controlling its formation are also presented. synthesis of the latter was found to be inhibited by adenosine in Aerobacter aero genes (10) and adenine in Salmonella typhimurium (9). On the other hand it was reported by Diorio et al (11) that purines did not inhibit production of pyrimidine precursor compounds by Neurospora crassa, furthermore that some purine antagonists stimulated their pro duction.…”