Manganese superoxide dismutase function

CL Eisher, J-L Chen, J Li, D Bashford, L Noodleman. Density-functional and electrostatic calculations for a model of a manganese superoxide dismutase active site in aqueous solution. J Phys Chem 100 13498-13505, 1996. 

Hence, (Cl8TPP)Fe and (Cl8TPP)Mn facihtate the disproportionation of 02, which is equivalent to the function of the iron and manganese superoxide dismutase proteins. 

Fig. 2. (a) Structure and function of H. sapiens manganese superoxide dismutase (PDP-code lABM) and (b) synthetic low molecular weight substitute of MnSOD optimized for therapeutical purposes (20). 

Hence, (ClgTPP)Fell (ClgTPP)Mnll facilitate the disproportionation of O2 -, which is equivalent to the function of the iron and manganese superoxide dismutase proteins. Whether the mechanism of Eq. (7-28) is relevant to those for the proteins is unknown, but the absence of electron transfer from their metal centers to O2 - is a reasonable expectation (as is radical-radical coupling of 02"-and the protein in the primary step of the disproportionation mechanism). 

Guan Y, Hickey MJ, Borgstahl GE, Hallewell RA, Lepock JR, O Connor D, Hsieh Y, Nick HS, Silverman DN and Tainer JA (1998) Crystal structure of Y34F mutant human mitochondrial manganese superoxide dismutase and the functional role of tyrosine 34. Biochemistry 37 4722-4730. 

M.S. Lah, M.M. Dixon, K.A. Pattridge, W.C. Stallings, J.A. Fee, and M.L. Ludwig, Structure-function in Escherichia coli iron superoxide dismutase comparisons with the manganese enzyme from Thermus thermophilus. Biochemistry. 34, 1646-1660 (1995). 

Manganese performs significant antioxidative functions. It is included in the structure of Mn-dependent superoxide dismutase which is the only antioxidant based directly in the mitochondria where the intensive processes of oxidation and ATP synthesis occur. The Mn-dependent superoxide dismutase protects the mitochondria from oxidant stress. 

Manganese is the third most abundant transition element [1]. It is present in a number of industrial, hiological, and environmental systems, representative examples of which include manganese oxide batteries [2] the oxygen-evolving center of photosystem II (PSII) [3] manganese catalase, peroxidase, superoxide dismutase (SOD), and other enzymes [4, 5] chiral epoxidation catalysts [6] and deep ocean nodules [7]. Oxidation-reduction chemistry plays a central role in the function of most, if not all, of these examples. 

The most common metal encountered in electron transfer systems is iron, although copper and manganese play vital functions. Merely to emphasise the complexity of the catalysts that are used in biology, the structures of the active sites of ascorbate oxidase (Fig. 10-11) and superoxide dismutase (Fig. 10-12) are presented. It is clear that we have only just begun to understand the exact ways in which metal ions are used to control the reactivity of small molecules in biological systems. 

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