Journal
IUBMB LIFE
Volume 63, Issue 1, Pages 21-25Publisher
WILEY
DOI: 10.1002/iub.409
Keywords
O-2-consumption; flavoprotein; detoxifying enzyme; oxidative stress; cell proteolysis; protozoan pathogen
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Funding
- Ministero dell'Istruzione, dell'Universita e della Ricerca of Italy [2008FJJHKM_002, RBFR08F41U_001]
- European Society of Clinical Microbiology and Infectious Diseases [2009]
- Regione Autonoma della Sardegna
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Giardia intestinalis is the microaerophilic protozoon causing giardiasis, a common infectious intestinal disease. Giardia possesses an O-2-scavenging activity likely essential for survival in the host. We report that Giardia trophozoites express the O-2-detoxifying flavodiiron protein (FDP), detected by immunoblotting, and are able to reduce O-2 to H2O rapidly (similar to 3 mu M O-2 x min x 10(6) cells at 37 degrees C) and with high affinity (C-50 = 3.4 +/- 0.7 mu M O-2). Following a short-term (minutes) exposure to H2O2 >= 100 mu M, the O-2 consumption by the parasites is irreversibly impaired, and the FDP undergoes a degradation, prevented by the proteasome-inhibitor MG132. Instead, H2O2 does not cause degradation or inactivation of the isolated FDP. On the basis of the elevated susceptibility of Giardia to oxidative stress, we hypothesize that the parasite preferentially colonizes the small intestine since, compared with colon, it is characterized by a greater capacity for redox buffering and a lower propensity to oxidative stress. (C) 2011 IUBMB IUMBM Life, 63(1): 21-25, 2011
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