REARRANGEMENT REACTIONS IN THE BIOSYNTHESIS OF MOLYBDOPTERIN - AN NMR-STUDY WITH MULTIPLY C-13 N-15 LABELED PRECURSORS/

The genes moaABC of Escherichia coli were ligated into the expression vector pNCO113. The resulting plasmid was transformed into a moeA muta nt of E. coli. From cultures of the recombinant strain, a pteridine de signated compound Z could be isolated at 5 mg/liter. Compound Z is a p roduct of precursor Z, a biosynthetic precursor of molybdopterin. Cult ures of the recombinant E. coli strain were supplied with [U-C-13(6)]g lucose, [U-C-13(5)]ribulose 5-phosphate, or [7-N-15,8-C-13]guanine. Th e culture medium also contained a large excess of unlabeled glucose. C ompound Z as well as nucleosides obtained by hydrolysis of RNA were is olated from the bacterial cultures, and their heavy isotope distributi on was investigated by one-dimensional and two-dimensional NMR spectro scopy. 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 an d 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 derivati ve. The remodeling of the carbon skeleton of the pentose and purine mo ieties proceed via intramolecular rearrangement reactions.