Tris(picolinato)manganese(II): a chemical model for the mechanism and function of mitochondrial superoxide dismutase.
The reaction of HO2. with the allylic groups of lipids initiates their peroxidation and auto-oxidation, and probably represents the most serious biological hazard of O2.- -derived species. The presence of tris(picolinato)manganese(II) [MnII(PA)2(PAH)(H2O)], a model complex for mitochondrial superoxide dismutase, (i) efficiently catalyzes the disproportionation of O2.-, (ii) precludes the formation HO2., and thereby (iii) prevents hydrogen abstraction from allylic and thiol groups. Such protection demonstrates that a primary function of superoxide dismutase is to block the formation of HO2., which is the obligatory intermediate for the nonenzymatic proton-induced disproportionation process. This requires that the primary step for the enzyme-O2.- reaction be kinetically favored and dominant relative to the protonation reaction (HA + O2.-).
D001554:Benzene; D055598:Chemical Phenomena; D002621:Chemistry; D003510:Cyclohexanes; D053138:Cyclohexenes; D008054:Lipid Peroxides / Q000378:metabolism; D008345:Manganese; D008928:Mitochondria / Q000201:enzymology*; D008954:Models, Biological; D009942:Organometallic Compounds; D013053:Spectrophotometry; D013482:Superoxide Dismutase / Q000378:metabolism*; D013481:Superoxides / Q000378:metabolism
D003510:Cyclohexanes; D053138:Cyclohexenes; D008054:Lipid Peroxides; D009942:Organometallic Compounds; C048401:1,4-cyclohexadiene; C048400:tris(picolinato)manganese(II); D013481:Superoxides; D008345:Manganese; D013482:Superoxide Dismutase; D001554:Benzene; C034005:1,3-cyclohexadiene