Biosynthesis of vitamin B 6 . Direct evidence for the mode of incorporation of C 3 -units derived from D -[U- 13 C 6 ]glucose

The 13C n.m.r. spectrum of a sample of pyridoxol, derived biosynthetically from D-[U-13C6]glucose in Escherichia coli, shows that C-2–C-3 and C-4–C-5 of the pyridine nucleus are the only two carbon–carbon bonds of pyridoxol which are generated de novo in the course of its biosynthesis from glucose, constituting direct evidence in support of the biogenetic scheme which we had proposed on the basis of earlier investigations with radioactive tracers.