期刊
ARCHIVES OF BIOCHEMISTRY AND BIOPHYSICS
卷 488, 期 1, 页码 9-13出版社
ELSEVIER SCIENCE INC
DOI: 10.1016/j.abb.2009.06.011
关键词
Oxidative/nitrosative stress; Metalloenzymes; Nitric oxide; O-2 detoxification; Anaerobic protozoa; Molecular evolution; Redox titration; Flavin; Reactive oxygen species; Substrate selectivity
资金
- Fundacao Para a Ciencia e Tecnologia of Portugal [PTDC/BIA-PRO/67267/2006, REEQ/336/BIO/2005]
- Ministero dell'Istruzione [SFRH/BPD/26895/2006]
- dell'Universita e della Ricerca of Italy
- European Society of Clinical Microbiology and Infectious Diseases
- Fundação para a Ciência e a Tecnologia [SFRH/BPD/26895/2006] Funding Source: FCT
Flavodiiron proteins (FDPs) are enzymes identified in prokaryotes and a few pathogenic protozoa, which protect microorganisms by reducing O-2 to H2O and/or NO to N2O. 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 +/- 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. (C) 2009 Elsevier Inc. All rights reserved.
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