Purification and biochemical characterization of a heme containing peroxidase from the human parasite P. falciparum

Abstract

A peroxidase (30 kDa) has been purified from the human malaria parasite Plasmodium falciparum to its homogeneity. The protein is a dimer of 15 kDa subunit as evident from SDS–PAGE and MALDI–TOF mass analysis. The antibodies developed against the purified protein cross-react selectively with this protein present in parasite lysate. It is a heme containing peroxidase [R/Z value (A₄₀₈/A₂₇₈) = 2.33] showing characteristic heme spectra with Soret peak at 408 nm and visible peaks at 536 and 572 nm. Analysis of Soret spectra in presence or absence of cyanide or azide reveals that iron of heme is in Fe-III state. Circular dichroism spectral analysis establishes that this protein contains mainly α-helix (60–70%). H₂O₂ interacts with the heme moiety of the enzyme as evidenced by optical difference spectroscopy and spectral studies indicate the formation of catalytically active peroxidase–H₂O₂ complex (Soret peak at 413 nm) to exhibit peroxidase activity. During the erythrocytic stages of its life cycle, the parasite is exposed to oxidative stress. As the parasite is susceptible to oxidative stress, this peroxidase may offer antioxidant role by scavenging endogenous H₂O₂.