Redox properties of the oxygen-detoxifying flavodiiron protein from the human parasite Giardia intestinalis.
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/vis 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+/-15mV and E(2)=-83+/-15mV), 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+/-20mV and E(2)=+2+/-20mV). 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.
Vicente
João B
JB
Instituto de Tecnologia Quimica e Biologica, Universidade Nova de Lisboa, Oeiras, Portugal.
Testa
Fabrizio
F
Mastronicola
Daniela
D
Forte
Elena
E
Sarti
Paolo
P
Teixeira
Miguel
M
Giuffrè
Alessandro
A
D000042:Absorption; D000818:Animals; D003067:Coenzymes / Q000378:metabolism; D004578:Electron Spin Resonance Spectroscopy; D005486:Flavin Mononucleotide / Q000378:metabolism; D016829:Giardia lamblia / Q000201:enzymology*; D006801:Humans; D007501:Iron / Q000378:metabolism*; D010084:Oxidation-Reduction; D010100:Oxygen / Q000302:isolation & purification / Q000378:metabolism*; D010271:Parasites / Q000201:enzymology; D015800:Protozoan Proteins / Q000378:metabolism*; D013379:Substrate Specificity; D017186:Titrimetry
D003067:Coenzymes; D015800:Protozoan Proteins; D005486:Flavin Mononucleotide; D007501:Iron; D010100:Oxygen