Bernard Estramareix

The biosynthesis of thiamine. Syntheses of [1,1,1,5-2H4]-1-deoxy-D-threo-2-pentulose and incorporation of this sugar in biosynthesis of thiazole by Escherichia coli cells

Non-growing, washed cells of Escherichia coli, depressed for the synthesis of thiamine, were incubated in the presence of [1,1,1,5-2H4]-1-deoxy-D-threo-2-pentulose (9) in a medium containing the pyrimidine moiety of thiamine, L-tyrosine, and glucose. The thiamine thus biosynthesized was extracted and cleaved to give 5-(2-hydroxyethyl)-4-methylthiazole (HET) which was examined as the trifluoroacetate derivative by electron-impact mass spectrometry. The distribution of the label in the fragments indicated that the pentulose (9) was a precursor of the C5-chain of HET without C–C bond cleavage. Several routes to 1-deoxypentuloses are described. Condensation of 2,4-O-benzylidene-D-[4-2H1]threose (23) with trideuteriomethylmagnesium iodide gave the protected 1-deoxypentitols (24) and (25). Brominolysis of the mixed dibutylstannylidenes then afforded [1,1,1,5-2H4]-3,5-O-benzylidene-1-deoxy-D-threo-2-pentulose (26), which was converted into the free sugar (9) by acidic hydrolysis. 1-Deoxy-D-erythro-2-pentulose was prepared in similar manner. Condensation of 2-([2H3]-methyl)-1,3-dithian with 2,3-O-isopropylidene-D-glyceraldehyde, followed by a C-3 epimerization step also led, after deprotection, to a mixture of [1,1,1-2H3]-1-deoxy-D-erythro- and [1,1,1-2H3]-1-deoxy-D-threo-2-pentulose, (5) and (6).

La tyrosine, facteur de la biosynthèse du thiazole de la thiamine chez Escherichia coli

Abstract De-repressed washed cells of a tyrosine auxotroph mutant of Eschericiacoli have exhibited a requirement for l -tyrosine to synthesize the thiazole moiety of thiamin. A close relationship between the amount of thiazole synthesized and the amount of l -tyrosine added to the medium was found. The label of a single carbon of tyrosine was incorporated into the thiazole of thiamin: namely that of the asymetric carbon which was incorporated into the C-2 of the thiazole moiety with a dilution of 50%. This incorporation of tyrosine with dilution by a tyrosine auxotroph organism indicates that tyrosine contributes to the pool of a precursor of the thiazole of thiamin. It is not entirely understood how tyrosine acts as an indispensable factor in thiamin biosynthesis.

The origin of the carbon chain in the thiazole moiety of thiamine in Escherichia coli: Incorporation of deuterated 1-deoxy-D-threo-2-pentulose

Abstract Non growing washed cells of Escherichia coli, derepressed for the biosynthesis of thiamine, have been incubated in the presence of glucose and either 1-deoxy- D -threo-2-pentulose 1 or 1-deoxy- D -erythro-2-pentulose 2 trideuterated on the methyl group. The incorporation of deuterium into the thiazole moiety of thiamine was measured by mass spectrometry. The label of the threo-compound was found in more than 40% of the thiazole biosynthesized in its presence; the label of the erythro-compound in less than 5%. Hence it is likely that the carbon chain of 1-deoxy- D -threo-2-pentulose is the precursor of the five carbons chain of the thiazole moiety of the thiamine molecule in E. coli.

Isolation of 5-(β-hydroxyethyl)-4-methylthiazole-2-carboxylic acid, a metabolite related to thiamine biosynthesis in Escherichia coli

Abstract Cells of Escherichia coli derepressed for thiamine biosynthesis excrete a new growth factor for a thiazole-less E. coli mutant. This factor has been identified as 5-(β-hydroxyethyl)-4-methylthiazole-2-carboxylic acid. This compound, though being closely connected to the biosynthesis of the thiazole moiety of thiamine, is likely not a precursor.

Sugars and Nucleotides and the Biosynthesis of Thiamine

Publisher Summary This chapter describes the various aspects of sugars and nucleotides and the biosynthesis of thiamine. Thiamine is present in cells as a free form, as the diphosphate and as the diphosphate of the hydroxyethyl derivative, in variable ratio. Thiamine can be considered to be the product of the quaternization of 4-methyl-5-(2-hydroxymethyl)thiazole by an active derivative of 4-amino-5-(hydroxymethyl)-2-methyl pyrimidine. The treatment of thiamine in aqueous solution with sodium hydrogensulfite achieves a quantitative separation of the two heterocyclic moieties to produce thiazole and the sodium salt of the sulfonic acid. It is found that if the pentose phosphates are indeed the precursors of the five-carbon chain of thiazole, it seems fairly obvious that the carbonyl group will participate in building the heterocyclic ring. Thus, carbon atoms C-1, C-2, and C-5 of the sugar would be the respective precursors of the methyl, C-2, and C-8 carbon atoms of the thiamine thiazole. Much less is known about the participation of sugars in the biosynthesis of pyramine in yeasts, and although it has been proven that sugars can provide some carbon atoms, the exact nature of the more advanced intermediates of sugar origin is not yet clear. In the case of Escherichia coli , it is found that adenine and adenosine are inhibitory and the synthesis of thiamine can be derepressed by culture in their presence.