QM/MM study of the conversion of biliverdin into verdoheme by heme oxygenase

Investigation of different substitutions, structure, charge and multiplicity spin of the iron verdoheme-rat heme oxygenase complex: a DFT study

Heme oxygenase-1 (HO-1) is an inducible stress protein that degrades heme to carbon monoxide, iron and biliverdin, which subsequently reduces to bilirubin. Many parameters of verdoheme–rat heme oxygenase complex structure and their role and function on heme degradation were unknown. In this work the structure of iron verdoheme in complex with rat heme oxygenase was studied by density functional theory based B3LYP method and 6-31G basis set. The main goal is to obtain structural and energetic information for various transition states and intermediates on reaction pathways. The charge of verdoheme and iron as the central metal, electron distribution, spin multiplicity of the molecule and proximal substituents effect on the verdoheme ring stabilization and their arrangement are discussed. Gas phase computation has shown that the central metal of the five coordinated rat-verdohemeas ferrous (Fe[Formula: see text] (from 1a-1i) and ferric (Fe[Formula: see text] (from 1j–1q). The Mulliken and NBO charge and spin calculation show that iron is considered as ferrous in all of the optimized structures. Assessment results can gain valuable chemical insight into the electronic reorganization during the reactions.