QM/MM study of the insertion of metal ion into protoporphyrin IX by ferrochelatase.
Ferrochelatase catalyzes the metallation of protoporphyrin IX in the terminal step of heme biosynthesis. Mutations in the ferrochelatase gene can lead to the disease erythropoietic porphyria. The catalyzing mechanism of ferrochelatase is still not fully understood. In this paper, we have studied the insertion of Fe(2+) into the protoporphyrin IX ring by Bacillussubtilis ferrochelatase using combined quantum mechanical and molecular mechanics (QM/MM) calculations. Geometries were optimized at the BP86/6-31G * level and energies were calculated at the B3LYP/TZVP level. The overall process involves the stepwise displacement of Glu-264, His-183, and a water molecule from Fe(2+), and the removal of two protons from the porphyrin ring. The rate-determining step is the cleavage of the bond between the oxygen atom of Glu-264 and Fe(2+), concomitant with the formation of the first Fe-N bond. It has an energy barrier of 57 kJ mol(-1). The porphyrin ring is only slightly distorted in the enzyme active site. The residue Tyr-13 plays a key role for the catalytic process extracting two protons from protoporphyrin IX.
School of Chemistry and Chemical Engineering, Sun Yat-Sen University, 510275 Guangzhou, PR China.
Yaxue
Y
Wang
Yong
Y
Shen
Ulf
U
Ryde
D001412:Bacillus subtilis / Q000201:enzymology; D002384:Catalysis; D005294:Ferrochelatase / Q000737:chemistry*; D007501:Iron / Q000737:chemistry*; D055595:Mechanical Phenomena; D008956:Models, Chemical; D008958:Models, Molecular; D011524:Protoporphyrins / Q000737:chemistry*; D011789:Quantum Theory
D011524:Protoporphyrins; C028025:protoporphyrin IX; D007501:Iron; D005294:Ferrochelatase