1. Role of proximal methionine residues in Leishmania major peroxidase
- Author
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Yadav, Rajesh K., Pal, Swati, Dolai, Subhankar, and Adak, Subrata
- Subjects
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METHIONINE , *LEISHMANIA , *PEROXIDASE , *CYTOCHROME c , *MUTAGENESIS , *GENETIC mutation , *PORPHYRINS - Abstract
Abstract: The active site architecture of Leishmania major peroxidase (LmP) is very similar with both cytochrome c peroxidase and ascorbate peroxidase. We utilized point mutagenesis to investigate if the conserved proximal methionine residues (Met248 and Met249) in LmP help in controlling catalysis. Steady-state kinetics of methionine mutants shows that ferrocytochrome c oxidation is <2% of wild type levels without affecting the second order rate constant of first phase of Compound I formation, while the activity toward a small molecule substrate, guaiacol or iodide, increases. Our diode array stopped-flow spectral studies show that the porphyrin π-cation radical of Compound I in mutant LmP is more stable than wild type enzyme. These results suggest that the electronegative sulfur atoms of the proximal pocket are critical factors for controlling the location of a stable Compound I radical in heme peroxidases and are important in the oxidation of ferrocytochrome c. [Copyright &y& Elsevier]
- Published
- 2011
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