title: Reactivity of manganese peroxidase: site-directed mutagenesis of residues in proximity to the porphyrin ring.
abstract: The purpose of this study was to determine the effect of heme pocket hydrophobicity on the reactivity of manganese peroxidase. Residues within 5 A of the heme active site were identified. From this group, Leu169 and Ser172 were selected and mutated to Phe and Ala, respectively. The mutant proteins were then characterized by steady-state kinetics. Whereas the Leu169Phe mutation had little, if any, effect on activity, the Ser172Ala mutation decreased kcat and also the specificity constant (kcat/Km) for Mn2+, but not H2O2. Transient-state studies indicated that the mutation affected only the reactions of compound II. These results indicate that compound II is the most sensitive to changes in the heme environment.
authors.affiliation: Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park 16802, USA.
authors.forename: K
authors.initials: K
authors.lastname: Ambert-Balay
authors.forename: M
authors.initials: M
authors.lastname: Dougherty
authors.forename: M
authors.initials: M
authors.lastname: Tien
mesh_terms: D000409:Alanine / Q000737:chemistry; D001665:Binding Sites; D018076:DNA, Complementary / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004926:Escherichia coli / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000494:pharmacology; D007700:Kinetics; D007930:Leucine / Q000737:chemistry; D008956:Models, Chemical; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D010544:Peroxidases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D010649:Phenylalanine / Q000737:chemistry; D011166:Porphyrins / Q000737:chemistry; D017510:Protein Folding; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D012694:Serine / Q000737:chemistry; D013816:Thermodynamics
chemical_list: D018076:DNA, Complementary; D011166:Porphyrins; D011994:Recombinant Proteins; D012694:Serine; D010649:Phenylalanine; D006861:Hydrogen Peroxide; D010544:Peroxidases; C051129:manganese peroxidase; D007930:Leucine; D000409:Alanine