title: Effect of modified hemes on the spectral properties and activity of manganese peroxidase.
abstract: Recombinant manganese peroxidase (rMnP), expressed in Escherichia coli as apo-protein, was constituted with Fe(III) protoporphyrin IX, Fe(III) protoporphyrin IX dimethyl ester (DME), Fe(III) deuteroporphyrin (Deut), Fe(III) etioporphyrin III (Etio), and Fe(III) methylpyrrolporphyrin XXI (MPP). The electronic absorption spectra of these hemoproteins were similar to those of native MnP, but absorption maxima were shifted to longer wavelengths in the order of Deut-rMnP, MPP-rMnP, Etio-rMnP, DME-rMnP, and rMnP. All enzymes contained a high-spin, pentacoordinate heme iron as evidenced by the characteristic charge transfer bands in the visible region. The hemoproteins exhibited reduced catalytic activity while maintaining similar substrate Km values compared to native MnP. Compounds I, II, and III were obtained for these hemin-analogue enzymes except for Deut-rMnP. We concluded that the spectral properties of MnP are strongly influenced by porphyrin alpha- and beta-meso edge substituents and manganese oxidation is affected by the gamma-meso edge groups, suggesting a role for the heme propionates in electron transfer during catalysis.
authors.affiliation: Biotechnology Center, Utah State University, Logan, Utah, 84322-4705, USA.
authors.forename: N S
authors.initials: NS
authors.lastname: Reading
authors.forename: S D
authors.initials: SD
authors.lastname: Aust
mesh_terms: D004789:Enzyme Activation; D004926:Escherichia coli / Q000235:genetics; D005290:Ferric Compounds / Q000737:chemistry; D006418:Heme / Q000737:chemistry*; D007700:Kinetics; D010544:Peroxidases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D020075:Phanerochaete; D011524:Protoporphyrins / Q000737:chemistry; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000302:isolation & purification; D013056:Spectrophotometry, Ultraviolet
chemical_list: D005290:Ferric Compounds; D011524:Protoporphyrins; D011994:Recombinant Proteins; D006418:Heme; C028025:protoporphyrin IX; D010544:Peroxidases; C051129:manganese peroxidase