title: Formation of compound I and compound II ferryl species in the reaction of hemoglobin I from Lucina pectinata with hydrogen peroxide.
abstract: The formation of ferryl heme (Fe(IV) = O) species, i.e., compound I and compound II, has been identified as the main intermediates in heme protein peroxidative reactions. We report stopped-flow kinetic measurements which illustrate that the reaction of hemoglobin I (HbI) from Lucina pectinata with hydrogen peroxide produce ferryl intermediates compound I and compound II. Compound I appears relatively stable displaying an absorption at 648 nm. The rate constant value (k'(2)) for the conversion of compound I to compound II is 3.0 x 10(-2) s(-1), more than 100 times smaller than that reported for myoglobin. The rate constant value for the oxidation of the ferric heme (k'(12) + k'(13)) is 2.0 x 10(2) M(-1) s(-1). These values suggest an alternate route for the formation of compound II (by k'(13)) avoiding the step from compound I to compound II (k'(2)). In HbI from L. pectinata the stabilization of compound I is attribute to the unusual collection of amino acids residues (Q64, F29, F43, F68) in the heme pocket active site of the protein.
authors.affiliation: Chemistry Department, University of Puerto Rico, Mayagüez Campus, Mayagüez, Puerto Rico 00681-9019.
authors.forename: W
authors.initials: W
authors.lastname: De Jesús-Bonilla
authors.forename: J E
authors.initials: JE
authors.lastname: Cortés-Figueroa
authors.forename: F A
authors.initials: FA
authors.lastname: Souto-Bachiller
authors.forename: L
authors.initials: L
authors.lastname: Rodríguez
authors.forename: J
authors.initials: J
authors.lastname: López-Garriga
mesh_terms: D000596:Amino Acids / Q000737:chemistry; D000818:Animals; D002374:Catalase / Q000378:metabolism; D005290:Ferric Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D005296:Ferrous Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D006454:Hemoglobins; D006455:Hemoglobins, Abnormal / Q000737:chemistry*; D006861:Hydrogen Peroxide / Q000737:chemistry*; D008974:Mollusca / Q000737:chemistry*; D013056:Spectrophotometry, Ultraviolet
chemical_list: D000596:Amino Acids; D005290:Ferric Compounds; D005296:Ferrous Compounds; D006454:Hemoglobins; D006455:Hemoglobins, Abnormal; C026236:hemoglobin I, non-mammalian; D006861:Hydrogen Peroxide; C038109:pseudocatalase; D002374:Catalase