title: Mitochondrial reduction of metmyoglobin: dependence on the electron transport chain.
abstract: Reduction of ferric myoglobin (metmyoglobin, MetMb) to its ferrous form is important for maintaining fresh meat color because only reduced myoglobin can bind oxygen to form the consumer-preferred cherry red color in fresh meat. The objective of this study was to characterize an apparent mitochondria electron transport chain (ETC)-linked pathway for MetMb reduction in vitro. MetMb was reduced in the presence of mitochondria and succinate (p < 0.05); mitochondria or succinate alone did not facilitate MetMb reduction relative to controls (p > 0.05). Flushing samples with oxygen greatly decreased MetMb reduction, while flushing with argon increased MetMb reduction when compared with controls (p < 0.05). ETC inhibitors were used to localize the site where electrons became available for MetMb reduction. MetMb reduction was increased by rotenone addition and decreased by malonic acid (p < 0.05); the reduction was completely abolished by additions of antimycin A or myxothiazol when compared with controls (p < 0.05). These results suggest that electrons become available for MetMb reduction at a site(s) between complex III and IV. Mitochondrial ETC-linked MetMb reduction increased with increased mitochondrial density and succinate concentration (p < 0.05); the greatest MetMb reduction was observed at pH 7.2 and 37 degrees C, and ETC-linked MetMb reducing activity decreased with time postmortem (p < 0.05). These results indicate that ETC-linked MetMb reduction exists but would be minimally active in postmortem muscles.
authors.affiliation: Department of Animal Science, University of Connecticut, Storrs, 06269-4040, USA.
authors.forename: Jiali
authors.initials: J
authors.lastname: Tang
authors.forename: Cameron
authors.initials: C
authors.lastname: Faustman
authors.forename: Richard A
authors.initials: RA
authors.lastname: Mancini
authors.forename: Mark
authors.initials: M
authors.lastname: Seyfert
authors.forename: Melvin C
authors.initials: MC
authors.lastname: Hunt
mesh_terms: D000818:Animals; D002417:Cattle; D045222:Electron Transport Chain Complex Proteins / Q000378:metabolism*; D006736:Horses; D006863:Hydrogen-Ion Concentration; D008460:Meat; D008786:Metmyoglobin / Q000378:metabolism*; D008929:Mitochondria, Heart / Q000378:metabolism*; D010084:Oxidation-Reduction; D010101:Oxygen Consumption; D011180:Postmortem Changes
chemical_list: D045222:Electron Transport Chain Complex Proteins; D008786:Metmyoglobin