δ-Aminolevulinate (ALA) Synthesis in Synechococcus 6301: Requirement for tRNAGlu, and Pyridoxamine Phosphate

In plants, algae, cyanobacteria and some other bacterial species 5-aminolevulinate (ALA) is synthesized from glutamate (1–6). This reaction sequence involves ligation of glutamate to a tRNAGlu species and subsequent reduction to glutamate-1-semialdehyde (GSA) (7). The conversion of GSA to ALA is then catalysed by GSA-aminotransferase (E.C. 5.4.3.8.) (2,8). Dependent on the requirement of pyridoxamine-phosphate (PAMP) or pyridoxal-phosphate (PALP) for activity, either 4,5-diaminovalerate (8–10) or 4,5-dioxovalerate (DOVA) (5,11,12) are proposed as intermediates.