title: Carbon monoxide binding to pentacoordinate mercaptide-heme complexes: kinetic study on models for cytochrome P-450.
abstract: Mercaptide anions form exclusively penta-coordinate heme complexes [RS-heme] in polar and nonpolar solution over a wide range of mercaptide concentration. These complexes have a Soret peak at 408 nm and a formation constant of about 2.5 X 10(4) M(-1), and combine with CO to give a CO-cytochrome P-450 type spectrum. Kinetics of CO binding to mercaptide-heme complexes [RS-heme] have been studied by the flash photolysis method. Characteristic constants for this reaction suggest close similarities between [CH3-(CH2)3-S-heme] and cytochrome P-450. The reaction of alkoxide anion with heme has also been examined but no evidence was found for the existence of the [RO-heme-CO[ species.
mesh_terms: D002248:Carbon Monoxide; D003577:Cytochrome P-450 Enzyme System; D006418:Heme; D007700:Kinetics; D008024:Ligands; D008956:Models, Chemical; D010084:Oxidation-Reduction; D013057:Spectrum Analysis; D013438:Sulfhydryl Compounds; D013816:Thermodynamics
chemical_list: D008024:Ligands; D013438:Sulfhydryl Compounds; D006418:Heme; D002248:Carbon Monoxide; D003577:Cytochrome P-450 Enzyme System