Synthesis of vitamin B6 by a mutant of Escherichia coli K12 and the action of 4'-deoxypyridoxine.

Mutants of Escherichia coli K12 blocked in the oxidation of pyridoxine 5'-phosphate ('Oxidase' mutants) excreted pyridoxine at an initial rate of 19 pmol h-1 (10(8) bacteria)-1, i.e.0.6 nmol h-1 (mg dry wt)-1, when starved for pyridoxal. Glycolaldehyde, L-phosphoserine, DL-serine and, to a lesser extent, L-leucine stimulated the rate of pyridoxine excretion, but there was no significant stimulation by 2'-hydroxypyridoxine. 4'-Deoxypyridoxine inhibited or stimulated growth of the "Oxidase' mutant, depending on the relative concentrations of added pyridoxal and 4'-deoxypyridoxine. It was concluded that stimulation of growth by 4'-deoxypyridoxine was due to its conversion to pyridoxal.