Fig. 1.

Both annotated C. reinhardtii heme oxygenases (HMOX1 and HMOX2) and PCYA bilin reductase genes encode catalytically active enzymes. (A) Tetrapyrrole pathways of C. reinhardtii and their perturbation by artificial introduction of mammalian biliverdin reductase (BVR). Feedback inhibition of tetrapyrrole synthesis by heme is indicated by a dotted line, and depletion of heme upon plastid expression of BVR is indicated by dashed lines. Chl, chlorophyll; PPIX, protoporphyrin IX. (B) HPLC elution profiles of HMOX metabolites and mixtures of BV isomers (α, δ, and β) obtained by chemical oxidative degradation of hemin. (C) HPLC analysis of PCYA-catalyzed formation of PCB from BV IXα and bilin standards (top traces). The asterisk indicates an impurity.