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The genes moaABC of Escherichia coli were ligated into the expression vector pNCO113. The resulting plasmid was transformed into a moeA mutant of E. coli. From cultures of the recombinant strain, a pteridine designated compound Z could be isolated at 5 mg/liter. Compound Z is a product of precursor Z, a biosynthetic precursor of molybdopterin. Cultures of the recombinant E. coli strain were supplied with U-(13)C6glucose, U-(13)C5ribulose 5-phosphate, or 7-(15)N,8-(13)Cguanine. The culture medium also contained a large excess of unlabeled glucose. Compound Z as well as nucleosides obtained by hydrolysis of RNA were isolated from the bacterial cultures, and their heavy isotope distribution was investigated by one-dimensional and two-dimensional NMR spectroscopy. The labelling patterns of compound Z show that the carbon atoms of a pentose or pentulose are diverted to the ring atoms C6 and C7 and to the side chain atoms C2', C3' and C4' of compound Z. Carbon atom C1' of compound Z is derived from carbon atom C8 of a guanine derivative. The remodeling of the carbon skeleton of the pentose and purine moieties proceed via intramolecular rearrangement reactions.
Rieder et al. (Wed,) studied this question.