Fig. 4 in Genomic insights into the biosynthesis and physiology of the cyanobacterial neurotoxin 2,4-diaminobutanoic acid (2,4-DAB)

Fig. 4. The biochemical pathway to schizokinen. The established route to rhizobactin 1021 in Sinorhizobium meliloti (Lynch et al., 2001) includes schizokinen as its immediate precursor. (The enzyme responsible for the biosynthesis of rhizobactin 1021 from schizokinen is currently unknown). Nomenclature is from www.bren da-enzymes.org. The genes rhbA and rhbB (Lynch et al., 2001), correspond to the enzymes diaminobutanoate-2-oxo-glutarate transaminase (RhbA, EC 2.6.1.76) and diaminobutanoate decarboxylase (RhbB, EC 4.1.1.86). The enzymes RhbD (an acetylase), RhbE (which catalyses the oxidation of a single amino group of 1,3-diaminopropane), RhbC and RhbF (which catalyse condensation reactions) are unclassified. Redrawn from Lynch et al. (2001). The molecule in square brackets* represents 2,4-diaminobutanoate (2,4-diaminobutanoic acid) after rotation of the amino and carboxylate functions about carbon-2 to allow visual alignment of the amino groups in 1,3-diaminopropane and subsequent derivatives.