EFFECT OF MODIFIED HEMES ON THE SPECTRAL PROPERTIES AND ACTIVITY OF MANGANESE PEROXIDASE

Recombinant manganese peroxidase (rMnP), expressed in Escherichia coli as ape-protein, was constituted with Fe(III) protoporphyrin IX, Fe(II I) protoporphyrin IX dimethyl ester (DME), Fe(III) deuteroporphyrin (D eut), Fe(III) etioporphyrin III (Etio), and Fe(III) methylpyrrolporphy rin MII (MPP). The electronic absorption spectra of these hemoproteins were similar to those of native MnP, but absorption maxima were shift ed to longer wavelengths in the order of Deut-rMnP, MPP-rMnP, Etio-rMn P, DME-rMnP, and rMnP. All enzymes contained a high-spin, pentacoordin ate heme iron as evidenced by the characteristic charge transfer bands in the visible region. The hemoproteins exhibited reduced catalytic a ctivity while maintaining similar substrate K-m values compared to nat ive MnP. Compounds I, II, and III were obtained for these hemin-analog ue enzymes except for Deut-rMnP. We concluded that the spectral proper ties of MnP are strongly influenced by porphyrin alpha- and beta-meso edge substituents and manganese oxidation is affected by the gamma-mes o edge groups, suggesting a role for the heme propionates in electron transfer during catalysis. (C) 1998 Academic Press.