Stable isotope evidence for the localisation of phenylalanine biosynthesis in the bacterium Paracoccus denitrificans

Paracoccus denitrificans was grown on [6-13C]-glucose as the sole carbon source for growth and the extracts were fractionated and analysed by gas chromatography-mass spectrometry. The 13C-labelling pattern observed in phenylalanine indicated that the biosynthetic sequences of enzymes for phenylalanine production were unequally distributed within the cell and that there are at least 2 separate loci of phenylalanine biosynthesis. The principal locus of phenylalanine production was associated with the Entner-Doudoroff and/or the pentose phosphate pathways and it was responsible for producing 3/4 of the bacterium's phenylalanine. A second locus was associated with the G6 oxidation pathway and was responsible for producing the remaining 1/4 of the cell's phenylalanine.