FIG. 1.

Proposed vitamin B₆ pathway in E. coli and S. meliloti. Abbreviations: GcolAD, glycolaldehyde; Gly, glycine; Pyr, pyruvate; GcerADP, d-glyceraldehyde 3-phosphate; GcerAD, d-glyceraldehyde. The 4PHT-1, 4PHT-2, DXP-1, DXP-2, and final pathways are pathways that result in the synthesis of 4PHT from E4P (E. coli), the synthesis of 4PHT from glycolaldehyde and glycine via 4HT (S. meliloti), the synthesis of DXP from pyruvate and d-glyceraldehyde 3-phosphate (E. coli), the synthesis of DXP from pyruvate and d-glyceraldehyde via DX (S. meliloti), and the synthesis of PNP from 4PHT and DXP, respectively; these pathways are indicated by the areas enclosed by the dashed lines.