Characterization of biochemical properties of a selenium-independent glutathione peroxidase of Cryptosporidium parvum.
Glutathione peroxidase (GPx; EC 1.11.1.9) is an important antioxidant enzyme that catalyses the reduction of organic and inorganic hydroperoxides to water in oxygen-consuming organisms, using glutathione as an electron donor. Here, we report the characterization of a GPx of Cryptosporidium parvum (CpGPx). CpGPx contained a standard UGU codon for cysteine instead of a UGA opal codon for seleno-cysteine (SeCys) at the active site, and no SeCys insertion sequence (SECIS) motif was identified within the 3'-untranslated region (UTR) of CpGPx, which suggested its selenium-independent nature. In silico and biochemical analyses indicated that CpGPx is a cytosolic protein with a monomeric structure. Recombinant CpGPx was active over a wide pH range and was stable under physiological conditions. It showed a substrate preference against organic hydroperoxides, such as cumene hydroperoxide and t-butyl hydroperoxide, but it also showed activity against inorganic hydroperoxide, hydrogen peroxide. Recombinant CpGPx was not inhibited by potassium cyanide or by sodium azide. The enzyme effectively protected DNA and protein from oxidative damage induced by hydrogen peroxide, and was functionally expressed in various developmental stages of C. parvum. These results collectively suggest the essential role of CpGPx for the parasite's antioxidant defence system.
Department of Parasitology and Institute of Health Sciences, Gyeongsang National University School of Medicine, Jinju 660-751, Korea.
J-M
JM
Kang
Department of Parasitology and Institute of Health Sciences, Gyeongsang National University School of Medicine, Jinju 660-751, Korea.
H-L
HL
Ju
Department of Parasitology and Institute of Health Sciences, Gyeongsang National University School of Medicine, Jinju 660-751, Korea.
W-M
WM
Sohn
Department of Parasitology and Institute of Health Sciences, Gyeongsang National University School of Medicine, Jinju 660-751, Korea.
B-K
BK
Na
D000595:Amino Acid Sequence; D000818:Animals; D000913:Antibodies, Protozoan / Q000276:immunology*; D000975:Antioxidants / Q000378:metabolism; D003457:Cryptosporidiosis / Q000469:parasitology*; D016785:Cryptosporidium parvum / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics / Q000276:immunology; D003600:Cytosol / Q000201:enzymology; D005978:Glutathione / Q000378:metabolism; D005979:Glutathione Peroxidase / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D010802:Phylogeny; D011190:Potassium Cyanide / Q000494:pharmacology; D017434:Protein Structure, Tertiary; D015800:Protozoan Proteins / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins; D016415:Sequence Alignment; D019810:Sodium Azide / Q000494:pharmacology
D000913:Antibodies, Protozoan; D000975:Antioxidants; D015800:Protozoan Proteins; D011994:Recombinant Proteins; D019810:Sodium Azide; D006861:Hydrogen Peroxide; D005979:Glutathione Peroxidase; C080439:selenium-independent glutathione peroxidase; D005978:Glutathione; D011190:Potassium Cyanide