title: Proton linkage for CO binding and redox properties of bovine lactoperoxidase.
abstract: The pH-dependence of redox properties and of CO binding to bovine lactoperoxidase has been investigated over the range between 2 and 11. The pH-dependence of redox potentials shows a biphasic behavior, suggesting the existence of (at least) two redox-linked groups, which change their pKa values upon reduction. These values are in close agreement with those observed to play a relevant role in the modulation of CO binding to ferrous bovine lactoperoxidase. They have been tentatively attributed to Arg-372 and His-226, which are located on the distal side of the heme pocket of lactoperoxidase. A complete and unequivocal description of the proton-linked behavior of bovine lactoperoxidase requires, however, three residues, which are redox linked and relevant for the modulation of CO binding. The rate constant for CO binding to bovine lactoperoxidase is slower than what is reported for most hemoproteins, suggesting that these two residues, Arg-372 and His-226, are representing a severe barrier for the access of exogenous ligands to the heme. This aspect has been further investigated by fast kinetics following laser photolysis, trying to obtain information on the ligand binding pathway and on the energy barriers.
authors.affiliation: Department of Experimental Medicine and Biochemical Sciences, Università di Tor Vergata, I-00133 Rome, Italy.
authors.forename: Chiara
authors.initials: C
authors.lastname: Ciaccio
authors.forename: Giampiero
authors.initials: G
authors.lastname: De Sanctis
authors.forename: Stefano
authors.initials: S
authors.lastname: Marini
authors.forename: Federica
authors.initials: F
authors.lastname: Sinibaldi
authors.forename: Roberto
authors.initials: R
authors.lastname: Santucci
authors.forename: Alessandro
authors.initials: A
authors.lastname: Arcovito
authors.forename: Andrea
authors.initials: A
authors.lastname: Bellelli
authors.forename: Elena
authors.initials: E
authors.lastname: Ghibaudi
authors.forename: Pia
authors.initials: P
authors.lastname: Ferrari Rosa
authors.forename: Massimo
authors.initials: M
authors.lastname: Coletta
mesh_terms: D000818:Animals; D001665:Binding Sites; D002248:Carbon Monoxide / Q000737:chemistry*; D002384:Catalysis; D002417:Cattle; D004789:Enzyme Activation; D006418:Heme / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D007784:Lactoperoxidase / Q000737:chemistry*; D008892:Milk / Q000737:chemistry; D010084:Oxidation-Reduction; D011485:Protein Binding; D011522:Protons
chemical_list: D011522:Protons; D006418:Heme; D002248:Carbon Monoxide; D007784:Lactoperoxidase