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Asian Journal of Animal Sciences
Year: 2011  |  Volume: 5  |  Issue: 2  |  Page No.: 145 - 152

Purification and Characterization of Plasmodium berghei Thioredoxin Reductase

G. Kapoor and H.S. Banyal    

Abstract: Present study was undertaken to purify and characterize thioredoxin reductase (TrxR) of Plasmodium berghei, a rodent malaria parasite. Plasmodium contains thioredoxin redox system that acts as efficient antioxidant system preventing damage caused by enhanced oxidative stress. Thioredoxin (Trx) functions as redox messenger in the parasite maintaining a reduced intracellular environment. Thioredoxin reductase (E.C.1.8.1.9) was analysed in rodent malaria parasite, Plasmodium berghei. Cell-free parasite showed TrxR specific activity of 0.128±0.10 U mg-1. Maximum TrxR activity was observed in cytosolic fraction of P. berghei. The parasite enzyme was purified by ammonium sulphate precipitation and Sephadex G-200. Its molecular weight was 22 kDa and the enzyme remained maximally active at pH 7.4 while the higher temperatures inactivated the enzyme. Km (Michaelis constant) and Vmax (Maximum velocity of enzyme) values for dithionitrobenzene (DTNB) substrate were 1.25 and 0.1 mM, respectively. 1-chloro-2, 4-dinitro benzene (CDNB) uncompetitively inhibited the enzyme substrate reaction and the inhibition was concentration dependent. Ki (inhibition constant) for CDNB was found to be 1.25 mM for 0.01 mM CDNB and 1.3 mM for 0.1 mM CDNB.

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