The Reactions of Heme- and Verdoheme-heme Oxygenase-1 Complexes with Fmn-depleted Nadph-cytochrome P450 Reductase. Electrons Required for Verdoheme Oxidation Can Be Transferred Through a Pathway Not Involving Fmn.
From: Department of Medical Biochemistry, Kurume University School of Medicine, Kurume 830-0011, Japan. higashiy@med.kurume-u.ac.jp
The Journal of biological chemistry
- Publish Date: Oct 2006
- ISSN: 0021-9258
- Volume: 281
- Issue: 42
- Pages: 31659-67
- Medium: Print
- Language: English
- Citation (JAMA): Higashimoto Yuichiro, Sato Hideaki, Sakamoto Hiroshi, et al. The Reactions of Heme- and Verdoheme-heme Oxygenase-1 Complexes with Fmn-depleted Nadph-cytochrome P450 Reductase. Electrons Required for Verdoheme Oxidation Can Be Transferred Through a Pathway Not Involving Fmn.. J. Biol. Chem. Oct 2006;281:31659-67
Abstract
Electrons utilized in the heme oxygenase (HO) reaction are provided by NADPH-cytochrome P450 reductase (CPR). To investigate the electron transfer pathway from CPR to HO, we examined the reactions of heme and verdoheme, the second intermediate in the heme degradation, complexed with rat HO-1 (rHO-1) using a rat FMN-depleted CPR; the FMN-depleted CPR was prepared by dialyzing the CPR mutant, Y140A/Y178A, against 2 m KBr. Degradation of heme in complex with rHO-1 did not occur with FMN-depleted CPR, notwithstanding that the FMN-depleted CPR was able to associate with the heme-rHO-1 complex with a binding affinity comparable with that of the wild-type CPR. Thus, the first electron to reduce the ferric iron of heme complexed with rHO-1 must be transferred from FMN. In contrast, verdoheme was converted to the ferric biliverdin-iron chelate with FMN-depleted CPR, and this conversion was inhibited by ferricyanide, indicating that electrons are certainly required for conversion of verdoheme to a ferric biliverdin-iron chelate and that they can be supplied from the FMN-depleted CPR through a pathway not involving FMN, probably via FAD. This conclusion was supported by the observation that verdoheme dimethyl esters were accumulated in the reaction of the ferriprotoporphyrin IX dimethyl ester-rHO-1 complex with the wild-type CPR. Ferric biliverdin-iron chelate, generated with the FMN-depleted CPR, was converted to biliverdin by the addition of the wild-type CPR or desferrioxamine. Thus, the final electron for reducing ferric biliverdin-iron chelate to release ferrous iron and biliverdin is apparently provided by the FMN of CPR.
Mesh Headings (Keywords): Animals, Binding Sites, Deferoxamine, Ferricyanides, Flavin Mononucleotide, Heme, Heme Oxygenase-1, Humans, Models, Chemical, Models, Molecular, Mutation, NADPH-Ferrihemoprotein Reductase, Rats
Check for Full Text / PubMed Unique Identifier (PMID): 16928691
This abstract is part of PubMed, a service of the U.S. National Library of Medicine. PubMed includes more than 17 million citations from MEDLINE and other life science journals for biomedical articles. See Copyright and Disclaimers.
Linked medical terms appearing on this page are added by Healia to help readers find more information and are not part of the original PubMed document.
The data herein was last updated on July 8th, 2008 and may not reflect the most current and accurate data available from NLM.