Protoporphyrin IX ferrochelatase

Figure 7.1 The overall pathway of haem biosynthesis. 5-AminolaevuIinate (ALA) is synthesized in the mitochondrion, and is transferred to the cytosol where it is converted to porphobilinogen, four molecules of which condense to form a porphyrin ring. The next three steps involve oxidation of the pyrrole ring substituents to give protoporphyrinogen fX, whose formation is accompanied by its transport back into the mitochondrion. After oxidation to protoporphyrin IX, ferrochelatase inserts Fe2+ to yield haem. A, P, M and V represent, respectively acetyl, propionyl, methyl and vinyl (—CH2=CH2) groups. From Voet and Voet, 1995. Reproduced by permission of John Wiley Sons, Inc.

Uroporphyrinogen decarboxylase catalyzes the conversion of uroporphyrinogen to coproporphyrinogen. The coporphyrinogen III can be oxidized to protoporphyrinogen IX, which is then oxidized to protoporphyrin IX. Ferrochelatase then inserts ferrous iron to form heme. The last three steps take place in the mitochondrion. 

Class 11 chelatases are small (30 40 kDa) monomeric or dimeric proteins and include protoporphyrin IX ferrochelatase (HemH), anaerobic cobalt chelatase (CbiK), and ferrochelatases of siroheme synthesis (CysG/Met8p) [21]. The cobalt chelatase CbiX is required for the biosynthesis of E12 and is found in archaea as a short form (CbiX 120-145 amino acids) and in some bacteria as a longer form (CbiX 300-350 amino acids) [21,22]. In Synechocystis PCC... 

In the first step of the heme branch, protoporphyrin IX ferrochelatase (FeCh) inserts Fe + into protoporphyrin IX to produce protoheme (Figure 5.37). Heme oxygenase catalyzes the oxidation and the ring opening of protoheme to give biliverdin EXa. This reaction is followed by the conversion to (3 )-phytochromobilin controlled by phytochromobilin synthase. Isomerization of 3 -phytochromobilin into the (3Z) isomer takes place before the chromophore is bound to the phytochrome apoprotein. Whether such an isomerization step is catalyzed by an enzyme or whether it proceeds spontaneously remained unknown [137]. 

---

See also in sourсe #XX -- [ ]

---