FIGURE 4.

Initial rates of zinc porphyrin formation catalyzed by 10 nm ferrochelatase. Assay conditions were 0.1 m Tris-HCl, pH 8.1, 0.5% Tween 20, with 0.5% (w/v) CHAPS at 30 °C. Filled circles represent experimental points at 35 μm D_IX with a theoretical line described by kinetic parameters V^app = 2.6 ± 0.2 nm s⁻¹ and K_m^app = 1.8 ± 0.8 μm. Open circles represent experimental points at 5 μm D_IX with a theoretical line described by kinetic parameters V^app = 1.3 ± 0.2 nm s⁻¹ and K_m^app = 4.5 ± 2.4 μm.