Fig. 6. Decarboxylase activity of wt AhbD with COPRO III as the substrate. The tetrapyrrole content in the assay mixtures was analyzed after 24 h of incubation at 17 °C by HPLC. The elution of the tetrapyrroles was monitored by measuring the absorption at 400 nm (solid line) and the fluorescence (dotted line, excitation at 409 nm, emission at 630 nm). Fe-COPRO III eluted at 20.9 min, the potential monovinyl intermediate at 30.1 min and heme at 37.5 min (top panel). COPRO III eluted at 25.7 min, the corresponding monovinyl intermediate at 34.5 min and PROTO IX at 40.5 min (lower panels). The respective monovinyl intermediates are highlighted by an asterisk.