Biosynthesis of vitamin B1 in yeast. Derivation of the pyrimidine unit from pyridoxine and histidine. Intermediacy of urocanic acid.

Incorporation studies with 13C-, 15N-, and 2H-labeled substrates, followed by NMR analysis, show that the pyrimidine unit of thiamin (Vitamin B1) originates from a C5N fragment, derived from C-2',2,N,C-6,5,5' of pyridoxol (Vitamin B6) and an N-C-N fragment derived from L-histidine. Urocanic acid serves as an intermediate on the route of the N-C-N fragment of histidine into the thiamin pyrimidine.

Biosynthesis of Vitamin B(6) in yeast. Incorporation pattern of trioses.

The biosynthetic origin of the C(3) unit, C-6,5,5', of pyridoxamine was investigated in two yeasts, Candida utilis ATCC 9256 and Saccharomyces cerevisiae ATCC 7752. The incorporation patterns within pyridoxamine bishydrochloride derived from variously multiply (13)C- and (2)H-labeled samples of glycerol and glyceraldehyde, established by NMR spectroscopy, indicate that the three-carbon unit C-6,5,5' of pyridoxamine is derived intact from a triose.

2'-hydroxypyridoxol, a biosynthetic precursor of vitamins B(6) and B(1) in yeast.

In separate experiments cultures of the yeast Saccharomyces cerevisiae ATTC 7752 were grown in the presence of [5',5'-2H2]- or of [2',2',5',5'-2H4]-3-hydroxy-2,4,5-tri(hydroxymethyl)pyridine (i.e., 2'-hydroxypyridoxol).

Biosynthesis of vitamin B(6) in yeast: incorporation pattern of glucose.

Two yeasts, Saccharomyces cerevisiae ATCC 7752 and Candida utilis ATCC 9256, were incubated in the presence of variously multiply (13)C-labeled samples of D-glucose. The (13)C incorporation pattern within pyridoxamine dihydrochloride, established by (13)C NMR spectroscopy, differed from that which had previously been found within pyridoxine, isolated from Escherichia coli. Thus, the origin of the carbon skeleton of vitamin B(6) in yeast differs substantially from its origin in E.

The biogenetic anatomy of vitamin B6. A 13C NMR investigation of the biosynthesis of pyridoxol in Escherichia coli.

It is shown by incorporation experiments with 13C bond-labeled substrates, followed by analysis by means of 13C NMR spectroscopy, that two compounds, 1-deoxy-D-xylulose (12) and 4-hydroxy-L-threonine (), serve as precursors of pyridoxol (vitamin B6) (1) in Escherichia coli. Together, these two compounds account for the entire C8N skeleton of the vitamin. 1-Deoxy-D-xylulose supplies the intact C5 unit, C-2',2,3,4,4' of pyridoxol.