title: A singular value decomposition approach for kinetic analysis of reactions of HNO with myoglobin.
abstract: The reactions of several horse heart myoglobin species with nitrosyl hydride, HNO, derived from Angeli's salt (AS) and Piloty's acid (PA) have been followed by UV-visible, (1)H NMR and EPR spectroscopies. Spectral analysis of myoglobin-derived speciation during the reactions was obtained by using singular value decomposition methods combined with a global analysis to obtain the rate constants of complex sequential reactions. The analysis also provided spectra for the derived absorbers, which allowed self-consistent calibration to the spectra of known myoglobin species. Using this method, the determined rate for trapping of HNO by metmyoglobin, which produces NO-myoglobin, is found to be 2.7 × 10(5)M(-1)s(-1) at pH7.0 and 1.1 × 10(5)M(-1)s(-1) at pH9.4. The reaction of deoxymyoglobin with HNO generates the adduct HNO-myoglobin directly, but is followed by a secondary reaction of that product with HNO yielding NO-myoglobin; the determined bimolecular rate constants for these reactions are 3.7 × 10(5)M(-1)s(-1) and 1.67 × 10(4)M(-1)s(-1) respectively, and are independent of pH. The derived spectrum for HNO-myoglobin is characterized by a Soret absorbance maximum at 423 nm with an extinction coefficient of 1.66 × 10(5)M(-1)cm(-1). The rate constant for unimolecular loss of HNO from HNO-myoglobin was determined by competitive trapping with CO at 8.9 × 10(-5)s(-1), which gives the thermodynamic binding affinity of HNO to deoxymyoglobin as 4.2 × 10(9)M(-1). These results suggest that the formation of HNO-ferrous heme protein adducts represents an important consideration in the biological action of HNO-releasing drugs.
authors.affiliation: Department of Chemistry and Biochemistry, Baylor University, Waco, TX 76796, USA.
authors.forename: Adrian L
authors.initials: AL
authors.lastname: Zapata
authors.forename: Murugaeson R
authors.initials: MR
authors.lastname: Kumar
authors.forename: Dmitry
authors.initials: D
authors.lastname: Pervitsky
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: Farmer
mesh_terms: D000818:Animals; D001667:Binding, Competitive; D002248:Carbon Monoxide / Q000737:chemistry; D004578:Electron Spin Resonance Spectroscopy; D006736:Horses; D006877:Hydroxamic Acids / Q000737:chemistry; D007700:Kinetics; D008786:Metmyoglobin / Q000737:chemistry*; D008956:Models, Chemical; D009206:Myocardium / Q000737:chemistry; D009211:Myoglobin / Q000737:chemistry*; D009573:Nitrites / Q000737:chemistry; D009589:Nitrogen Oxides / Q000737:chemistry*; D010084:Oxidation-Reduction; D011485:Protein Binding; D013449:Sulfonamides / Q000737:chemistry
chemical_list: D006877:Hydroxamic Acids; D009211:Myoglobin; D009573:Nitrites; D009589:Nitrogen Oxides; D013449:Sulfonamides; C055547:deoxymyoglobin; D008786:Metmyoglobin; C021229:oxyhyponitrite; C097220:Piloty's acid; D002248:Carbon Monoxide; C039900:nitroxyl