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. coli. In particular, in yeast the distribution of (13)C within the C(5) chain C-2',2,3,4,4' of pyridoxamine corresponds to the distribution of (13)C within the C(5) chain C-1,2,3,4,5 of the ribose component of cytidine. It follows that the C(5) chains of pyridoxamine and of ribose originate from a common glucose-derived pentulose or pentose intermediate. By contrast, in E. coli the C(5) chain of pyridoxine is derived from 1-deoxy-D-xylulose 5-phosphate which, in turn, originates by condensation of pyruvic acid with glyceraldehyde 3-phosphate.

The biogenetic hypothesis that the Lycopodium alkaloids are modified dimers of pelletierine (2, 3) was tested experimentally in Lycopodiumtristachyum, Pelletierine is indeed incorporated into lycopodine, but only one pelletierine unit entered the alkaloid, rather than two units, as predicted. The hypothesis thus requires modification.Δ1-Piperideine serves as a specific precursor of lycopodine. Two Δ1-piperideine moieties are incorporated in such a way that the identity of C-2 and -6 of each of the precursor units is maintained.

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.

The configuration of a metabolic precursor is determined experimentally by comparison of the 3H/14C ratio of the metabolic product with that of a doubly labeled substrate. This new method for the determination of precursor stereochemistry in intact systems does not depend on a comparison of incorporation efficiencies. It is shown by this method that the alkaloids sedamine, (V-methylpelletierine, and A-methylallosedridine from two Sedum species and anabasine from Nicotiana glauca are derived from L-lysine, whereas pipecolic acid, from each of these plants, is derived from D-lysine. 559 (1960).(6) E.g., incorporation of cystine into benzylpenicillin,7 of tryptophan into echinulin,8 actinomycin,9 and pyrrolnitrin,10 of valine and -hydroxyvaleric acid into valinomycin,11 of valine into benzylpenicillin,12,13 into sporidesmolide l,14 and into penicillin N and cephalosporin C,15 of tt-aminoadipic acid into penicillin N and cephalosporin C,16 of ornithine into bacitracin,17 of lysine into pipecolic acid,18•19 and of 5-hydroxylysine into 5-hydroxypipecolic acid.20