IQUIR   05412
INSTITUTO DE QUIMICA ROSARIO
Unidad Ejecutora - UE
capítulos de libros
Título:
Mn2+ and catalases
Autor/es:
SIGNORELLA, S.; PALOPOLI, C.; DAIER, V.; LEDESMA, G.
Libro:
Encyclopedia of Metalloproteins
Editorial:
Springer-Verlag
Referencias:
Lugar: New York; Año: 2013; p. 1283 - 1292
Resumen:
Manganese catalases are antioxidant enzymes that serve as the front line molecular defense against hydrogen peroxide in a number of organisms. The non-heme manganese containing catalases appear to be widespread among prokaryotes and have been isolated from bacteria (Thermus thermophilus, Thermoleophilum album, Salmonella enterica, Thermus sp and Lactobacillus plantarum), a hyperthermophilic archeon (Pyrobaculum caldifontis) and some cyanobacteria.  All known manganese catalase enzymes share an unusual bridged binuclear manganese cluster that serves as the active site to perform efficient two-electron disproportionation of hydrogen peroxide, interconverting between reduced and oxidized states during turnover.To efficiently catalyze the H2O2 disproportionation, the protein environment controls the reduction potential of the dimanganese active site to a value much lower than that of the Mn3+/Mn2+ couple. Besides, the presence of two Mn ions provides with a further tool to allow the protein to exchange more than one electron. These enzymes have developed a precise catalytic mechanism to disproportionate H2O2 without formation of hydroxyl radicals, where the ligands bridging the manganese ions and the protein environment surrounding the dimanganese center play a key role.