title: Role of proximal methionine residues in Leishmania major peroxidase.
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.
authors: Division of Structural Biology and Bio-informatics, Indian Institute of Chemical Biology, Council of Scientific and Industrial Research, 4, Raja S.C. Mullick Road, Kolkata, India.
authors: Rajesh K
authors: RK
authors: Yadav
authors: Swati
authors: S
authors: Pal
authors: Subhankar
authors: S
authors: Dolai
authors: Subrata
authors: S
authors: Adak
mesh_terms: D000818:Animals; D001483:Base Sequence; D045304:Cytochromes c / Q000378:metabolism; D017931:DNA Primers; D007700:Kinetics; D007891:Leishmania / Q000201:enzymology*; D008715:Methionine / Q000502:physiology*; D016297:Mutagenesis, Site-Directed; D010084:Oxidation-Reduction; D010544:Peroxidases / Q000737:chemistry / Q000378:metabolism*; D013056:Spectrophotometry, Ultraviolet
chemical_list: D017931:DNA Primers; D045304:Cytochromes c; D008715:Methionine; D010544:Peroxidases