Vicente JB, Testa F, Mastronicola D, Forte E, Sarti P, Teixeira M, Giuffrè A
Redox properties of the oxygen-detoxifying flavodiiron protein from the human parasite giardia intestinalis. [JOURNAL ARTICLE]
Arch Biochem Biophys 2009 Jun 19.
Flavodiiron proteins (FDPs) are enzymes identified in prokaryotes and a few pathogenic protozoa, which protect microorganisms by reducing O(2) to H(2)O and/or NO to N(2)O. Unlike most prokaryotic FDPs, the protozoan enzymes from the human pathogens Giardia intestinalis and Trichomonas vaginalis are selective towards O(2). UV/visible and EPR spectroscopy showed that, differently from the NO-consuming bacterial FDPs, the Giardia FDP contains an FMN with reduction potentials for the formation of the single and the two-electron reduced forms very close to each other (E(1)=-66+/-15 mV and E(2)=-83+/-15 mV), a condition favoring destabilization of the semiquinone radical. Giardia FDP contains also a non-heme diiron site with significantly up-shifted reduction potentials (E(1) = +163+/-20 mV and E(2) = +2+/-20 mV). These properties are common to the Trichomonas hydrogenosomal FDP, and likely reflect yet undetermined subtle structural differences in the protozoan FDPs, accounting for their marked O(2) specificity.
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