Heterolytic reduction of fatty acid hydroperoxides by cytochrome c/cardiolipin complexes: antioxidant function in mitochondria.
Cytochrome c (cyt c), a mitochondrial intermembrane electron shuttle between complexes III and IV, can, upon binding with an anionic phospholipid, cardiolipin (CL), act as a peroxidase that catalyzes cardiolipin oxidation. H(2)O(2) was considered as a source of oxidative equivalents for this reaction, which is essential for programmed cell death. Here we report that peroxidase cyt c/CL complexes can utilize free fatty acid hydroperoxides (FFA-OOH) at exceptionally high rates that are approximately 3 orders of magnitude higher than for H(2)O(2). Similarly, peroxidase activity of murine liver mitochondria was high with FFA-OOH. Using EPR spin trapping and LC-MS techniques, we have demonstrated that cyt c/CL complexes split FFA-OOH predominantly via a heterolytic mechanism, yielding hydroxy-fatty acids, whereas H(2)O(2) (and tert-butyl hydroperoxide, t-BuOOH) undergo homolytic cleavage. Computer simulations have revealed that Arg(38) and His(33) are important for the heterolytic mechanism at potential FFA-OOH binding sites of cyt c (but not for H(2)O(2) or t-BuOOH). Regulation of FFA-OOH metabolism may be an important function of cyt c that is associated with elimination of toxic FFA-OOH and synthesis of physiologically active hydroxy-fatty acids in mitochondria.
Belikova
Natalia A
NA
Center for Free Radical and Antioxidant Health and Department of Environmental and Occupational Health, University of Pittsburgh, 100 Technology Drive, Suite 350, Pittsburgh, Pennsylvania 15219-3130, USA.
Tyurina
Yulia Y
YY
Borisenko
Grigory
G
Tyurin
Vladimir
V
Samhan Arias
Alejandro K
AK
Yanamala
Naveena
N
Furtmüller
Paul Georg
PG
Klein-Seetharaman
Judith
J
Obinger
Christian
C
Kagan
Valerian E
VE
D000818:Animals; D000975:Antioxidants / Q000378:metabolism*; D031215:Armoracia / Q000201:enzymology; D002308:Cardiolipins / Q000378:metabolism*; D045304:Cytochromes c / Q000378:metabolism*; D005227:Fatty Acids / Q000378:metabolism*; D006861:Hydrogen Peroxide / Q000378:metabolism*; D008930:Mitochondria, Liver / Q000201:enzymology*; D008958:Models, Molecular; D051189:Murinae; D010084:Oxidation-Reduction; D011485:Protein Binding
D000975:Antioxidants; D002308:Cardiolipins; D005227:Fatty Acids; D045304:Cytochromes c; D006861:Hydrogen Peroxide