Fig. 1: Tetrapyrrole biosynthesis pathway. | Nature Communications

Fig. 1: Tetrapyrrole biosynthesis pathway.

From: Identification of Shemin pathway genes for tetrapyrrole biosynthesis in bacteriophage sequences from aquatic environments

Fig. 1

The common precursor 5-aminolevulinic acid (5-ALA) is synthesized by two different pathways. While plants, most bacteria and archaea use the C5 pathway employing glutamyl t-RNA reductase (GtrR) and glutamate-1-semialdehyde-2,1-aminomutase (GsaM), the aminolevulinic acid synthase (AlaS) within the Shemin pathway of alphaproteobacteria, mammals and birds condenses glycine and succinyl-CoA to yield 5-ALA. Eight molecules of 5-ALA are needed to synthesize intermediate uroporphyrinogen III, an intermediate to most modified tetrapyrroles. Heme can then be converted through heme oxygenase (HemO) to linear biliverdin IXα, which can be converted through ferredoxin-dependent bilin reductases to phycocyanobilin (PCB) or phycoerythrobilin (PEB). PcyA=phycocyanobilin:ferredoxin oxidoreductase; PebS/PcyX=phycoerythrobilin synthase; DHBV=dihydrobiliverdin. The side chains are abbreviated as follows: P=propionate; A=acetate; M=methyl; V=vinyl. Created with parts from BioRender.com, released under a Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International license.

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