Evidence for nonhydrogen bonded compound II in cyclic reaction of hemoglobin I from Lucina pectinata with hydrogen peroxide

Abstract

Studies that elucidate the behavior of the hemoglobins (Hbs) and myoglobins upon reaction with hydrogen peroxide are essential to the development of oxygen carrier substitutes. Stopped-flow kinetics and resonance Raman data show that the reaction between hydrogen peroxide and oxygenated and deoxygenated ferric Hb I (oxy- and deoxy-HbI) from Lucina pectinata produce compound I and compound II ferryl species. The rate constants ratio (k23/k41) between the formation of compound II from compound I (k23) and the oxidation of the ferrous HbI (k41, i.e., 25 M(-1) s(-1)) of 12 x 10(-4) M suggests that HbI has a peroxidative capacity for removing H2O2 from solution. Resonance Raman presents the formation of both, met-aquo-HbI and compound II ferryl species in the cyclic reaction of HbI with H2O2. The ferric HbI species is maintained by the presence of H2O2; it can produce HbI compound I, or it can be reduced to a deoxy-HbI derivative to form HbI compound II upon reaction with H2O2. The compound II ferryl vibration frequency appears at 805 and 769 cm(-1) for HbIFe(IV)=(16)O and HbIFe(IV)=(18)O species, respectively. This ferryl mode indicates the absence of hydrogen bonding between the carbonyl group of the distal Q64 and the HbIFe(IV)=O ferryl moiety. The observation suggests that both the trans-ligand effect and the polarizabilty of the HbI heme pocket are responsible for the observed ferryl oxo vibrational energy. The vibrational mode also suggests that the carbonyl group of the distal Q64 is oriented toward the iron of the heme group, increasing the distal pocket electron density.

Resonance Raman spectroscopy of oxoiron(IV) porphyrin π-cation radical and oxoiron(IV) hemes in peroxidase intermediates

“…851 cm À1 has been identified for O@Fe IV (salen), where salen is N,N 0 -ethylenebis(salicylideneaminato) anion [176]. For heme proteins, upper-end values for oxoiron(IV) stretching frequencies are 815 cm À1 for the ferryl form of heme d of cytochrome bd oxidase from E. coli [9,15], 805 cm À1 for the compound II form of hemoglobin I from Lucina pectinata [193], and 803 cm À1 for intermediates of cytochrome bo [7] and bovine heart cytochrome oxidase [194]. Low end m Fe(IV)@O values for protein-based ferryl hemes are 753 cm À1 (two overlapping components at 750 and 757 cm À1 ) for cytochrome c peroxidase compound ES, and 745 cm À1 for lactoperoxidase compound II [167].…”