title: Crystal structure and peroxidase activity of myoglobin reconstituted with iron porphycene.
abstract: The incorporation of an artificially created metal complex into an apomyoglobin is one of the attractive methods in a series of hemoprotein modifications. Single crystals of sperm whale myoglobin reconstituted with 13,16-dicarboxyethyl-2,7-diethyl-3,6,12,17-tetramethylporphycenatoiron(III) were obtained in the imidazole buffer, and the 3D structure with a 2.25-A resolution indicates that the iron porphycene, a structural isomer of hemin, is located in the normal position of the heme pocket. Furthermore, it was found that the reconstituted myoglobin catalyzed the H2O2-dependent oxidations of substrates such as guaiacol, thioanisole, and styrene. At pH 7.0 and 20 degrees C, the initial rate of the guaiacol oxidation is 11-fold faster than that observed for the native myoglobin. Moreover, the stopped-flow analysis of the reaction of the reconstituted protein with H2O2 suggested the formation of two reaction intermediates, compounds II- and III-like species, in the absence of a substrate. It is a rare example that compound III is formed via compound II in myoglobin chemistry. The enhancement of the peroxidase activity and the formation of the stable compound III in myoglobin with iron porphycene mainly arise from the strong coordination of the Fe-His93 bond.
authors.affiliation: Department of Applied Chemistry, Graduate School of Engineering, Osaka University, Suita 565-0871, Japan. thayashi@chem.eng.osaka-u.ac.jp
authors.forename: Takashi
authors.initials: T
authors.lastname: Hayashi
authors.forename: Dai
authors.initials: D
authors.lastname: Murata
authors.forename: Masatomo
authors.initials: M
authors.lastname: Makino
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Sugimoto
authors.forename: Takashi
authors.initials: T
authors.lastname: Matsuo
authors.forename: Hideaki
authors.initials: H
authors.lastname: Sato
authors.forename: Yoshitsugu
authors.initials: Y
authors.lastname: Shiro
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Hisaeda
mesh_terms: D000818:Animals; D001059:Apoproteins / Q000737:chemistry* / Q000378:metabolism*; D001555:Benzene Derivatives / Q000378:metabolism; D018360:Crystallography, X-Ray; D007501:Iron / Q000737:chemistry*; D008297:Male; D008665:Metalloporphyrins / Q000737:chemistry*; D008958:Models, Molecular; D015394:Molecular Structure; D009211:Myoglobin / Q000737:chemistry* / Q000378:metabolism*; D010544:Peroxidases / Q000378:metabolism*; D011166:Porphyrins / Q000737:chemistry*; D050661:Sperm Whale
chemical_list: D001059:Apoproteins; D001555:Benzene Derivatives; D008665:Metalloporphyrins; D009211:Myoglobin; D011166:Porphyrins; C010857:apomyoglobin; D007501:Iron; D010544:Peroxidases; C007164:cumene hydroperoxide