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8338255 
Journal Article 
Mechanisms for protection against inactivation of manganese peroxidase 
Fimofeevski, SL; Reading, NS; Ayst, SJ 
1998 
Yes 
FASEB Journal
ISSN: 0892-6638
EISSN: 1530-6860 
12 
8 
English 
It was previously observed for some heme p<>roxidases that their one-electron oxidized aromatic substrates can revert compound III, an inactive enzyme intermediate formed by reaction with excess hydrogen peroxide, back to ferric (active) enzym'. Here we report protection mechanisms for manganese peroxidase (MnP). known to oxidize Mri(II) complexed with oxalate or other appropriate carboxylic acid chelators to generate Mn(III). a powerful oxidant. Multiple turnover of MnP included several phases which can be explained by accumulation of compound III followed by its disappearance. The presence of Mn(III) appeared to stimulate MnP catalysis. When compound III was used to start the reaction. Mn(II) was also oxidized, but a !ag phase was observed. Accordingly, compound III was shown to yield ferric <*nzvrne by reaction with Mn(III). Such reaction with Mn(III) was not observed for lignin peroxidase or for recombinant MnP with the catalytic manganese site altered by modification of heme propionatos, suggesting that compound III of native MnP could interact with Mn(III) at the manganese site to oxidise iron-coordinated Superoxide via long-range c-Iectron transfer. Another protective mechanism for MnP involving Mn(III) is proposed for insufficient chelalor conditions. In contrast to effective Mn(II) chelators, ügands having low affinity for Mn(II), such as acetate or succinate. supported considerably slower MnP turnover, and Mn(III) released by the en/,yrne w.is more reactive with resprcî to hydrogen peroxide. The resulting catalase-typp activity may protect MnP frcmi 'uactivation by hydrogen peroxide wh'Ti oxala'e is limited.