Ferrochelatase (or protoporphyrin ferrochelatase) is an enzyme that is encoded by the FECH gene in humans. Ferrochelatase catalyses the eighth and terminal step in the biosynthesis of heme, converting protoporphyrin IX into heme B. It catalyses the reaction:

Ferrochelatase catalyzes the insertion of ferrous iron into protoporphyrin IX in the heme biosynthesis pathway to form heme B. The enzyme is localized to the matrix-facing side of the inner mitochondrial membrane. Ferrochelatase is the best known member of a family of enzymes that add divalent metal cations to tetrapyrrole structures. For example, magnesium chelatase adds magnesium to protoporphyrin IX in the first step of bacteriochlorophyll biosynthesis.

Heme B is an essential cofactor in many proteins and enzymes. In particular, heme b plays a key role as the oxygen carrier in hemoglobin in red blood cells and myoglobin in muscle cells. Furthermore, heme B is found in , a key component in (complex III) in oxidative phosphorylation.

Human ferrochelatase is a homodimer composed of two 359 amino acid polypeptide chains. It has a total molecular weight of 85.07 kDa. Each subunit is composed of five regions: a mitochondrial localization sequence, the N terminal domain, two folded domains, and a C terminal extension. Residues 1–62 form a mitochondrial localization domain that is cleaved in post-translational modification. The folded domains contain a total of 17 α-helices and 8 β-sheets. The C terminal extension contains three of the four cysteine residues (Cys403, Cys406, Cys411) that coordinate the catalytic iron-sulfur cluster (2Fe-2S). The fourth coordinating cysteine resides in the N-terminal domain (Cys196).

...
Wikipedia