Work

Crystal structure of Trypanosoma cruzi heme peroxidase and characterization of its substrate specificity and compound I intermediate

Year: 2022

Type: article

Abstract: The protozoan parasite Trypanosoma cruzi is the causative agent of American trypanosomiasis, otherwise known as Chagas disease. To survive in the host, the T. cruzi parasite needs antioxidant defense systems. One of these is a hybrid heme peroxidase, the T. cruzi ascorbate peroxidase-cytochrome c peroxidase enzyme ( Tc APx-C c P). Tc APx-C c P has high sequence identity to members of the class I peroxidase family, notably ascorbate peroxidase (APX) and cytochrome c peroxidase (C c P), as well as a mitochondrial peroxidase from Leishmania major ( Lm P). The aim of this work was to solve the structure and examine the reactivity of the Tc APx-C c P enzyme. Low temperature electron paramagnetic resonance spectra support the formation of an exchange-coupled [Fe(IV)=O Trp 233 •+ ] compound I radical species, analogous to that used in C c P and Lm P. We demonstrate that Tc APx-C c P is similar in overall structure to APX and C c P, but there are differences in the substrate-binding regions. Furthermore, the electron transfer pathway from cytochrome c to the heme in C c P and Lm P is preserved in the Tc APx-C c P structure. Integration of steady state kinetic experiments, molecular dynamic simulations, and bioinformatic analyses indicates that Tc APx-C c P preferentially oxidizes cytochrome c but is still competent for oxidization of ascorbate. The results reveal that Tc APx-C c P is a credible cytochrome c peroxidase, which can also bind and use ascorbate in host cells, where concentrations are in the millimolar range. Thus, kinetically and functionally Tc APx-C c P can be considered a hybrid peroxidase.

Source: Journal of Biological Chemistry

DOI: 10.1016/j.jbc.2022.102204