Manganese biochemical function

For iron, iodine, cobalt (as cobalamins), selenium, copper, and zinc there are clinical examples of reversible deficiency disease. For these elements there is enough known about their biochemical functions to explain their importance in human nutrition. For others, such as manganese, chromium, molybdenum, and vanadium, their importance remains to be fuUy accepted in clinical practice. Stfll other elements such as bromine, fluorine, cadmium, lead, strontium, lithium, and tin have been claimed by at least one investigator to be essential for one or more animal species as demonstrated by dietary deprivation studies. 

Problem 23.42. What is an important biochemical function of manganese ... 

Santucci R, Bongiovanni C, Marini S et al (2000) Redox equilibria of manganese peroxidase from Phanerochaete chrysosporium functional role of residues on the proximal side of the haem pocket. Biochem J 349 85-90... 

Figure 8.13. Equilibrium concentrations of biochemically important redox components as a function of pe at a pH of 7.0 (a) nitrogen (b) nitrogen, with elemental nitrogen N2 ignored (c) iron and manganese (d) sulfur (e) carbon. These equilibrium diagrams have been constructed from equilibrium constants listed in Tables 8.6a and 8.6b for the following concentrations Cr (total carbonate carbon) = 10 M [HjSCaq)) + [HS ] -I- [SOri = 10 M [NOj-] + [NOj"] + [NH ] = 10 M = 0.78 atm and thus [NjCaq)] = 0.5 x 10 M. For the construction of (b) the species NH4 , NOj, and NO are treated as metastable with regard to Nj.

Among the metal oxidation and reduction reactions that occur in the environment, the most intensely studied enzyme-catal5fzed reaction is the oxidation of divalent manganese. Bacteria and bacterial spores that carry out this function have been isolated from natural waters. These microbes are believed to produce proteins that enhance the rate, but the actual substances and the biochemical mechanism responsible for the reaction are not well characterized. 

Kuhn NJ, Ward S, Piponski M, et al. 1995. Purification of human hepatic arginase and its manganese (Il)-dependent and pH-dependent interconversion between active and inactive forms A possible pH sensing function of the enzyme on the ornithine cycle. Arch Biochem Biophys 320 24-34. 

Indeed, the biosynthesis of the biopolymer melanin involves the oxidative cyclization of dihydroxyphenylala-nine (DOPA) to phenylalanine-3,4-quinone (dopaquinone), which eventnally forms 5,6-dihydroxyindole (DHI). Polymerization of DHI affords melanin [1], Lim and Patil have exploited this biochemical transformation using commercial mushroom tyrosinase in a synthesis of 5,6-dihydroxyindoles protected as the diacetates (2) (Scheme 1) [2], The parent indole (R = R =H) is obtained in less than 10% yield. Carpender has reported a similar oxidative cyclization using manganese dioxide to give 2 (R =Me) in 80% overall yield from epinine (1, R =Me, R =H) [3]. Other oxidants (H, Hp /FeSO, O, NaOCl, NaClOj/ VjOj) gave little or no product. Choi, Nam, and colleagues have effected an electrochemical oxidation of dopamine (1, R = R =H) to 5,6-dihydroxyindole that polymerizes to form films of polydopamine suitable for neural attachment and function [4]. 

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