Biomaterial Database

Oxidation of yeast iso-1 ferrocytochrome c by yeast cytochrome c peroxidase compounds I and II. Dependence upon ionic strength. 1995

A L Matthis, and L B Vitello, and J E Erman

Department of Chemistry, Northern Illinois University, DeKalb 60115, USA.

The reduction of cytochrome c peroxidase compound I by excess yeast iso-1 ferrocytochrome c is biphasic. Two pseudo-first-order rate constants can be measured by stopped-flow techniques. The fastest rate process is the reduction of cytochrome c peroxidase compound I to compound II, and the slower process is the reduction of II to the native enzyme. The yeast iso-1 ferrocytochrome c concentration dependence of the reduction of cytochrome c peroxidase compound I to compound II is consistent with a mechanism involving two binding sites for cytochrome c on cytochrome c peroxidase. Electron transfer from cytochrome c bound at the high-affinity binding site to the Fe(IV) site in cytochrome c peroxidase compound I is dependent upon ionic strength, increasing from 15 +/- 6 to 2000 +/- 100 s-1 over the ionic strength range 0.01-0.20 M. The reduction rate of the Fe(IV) site in the 2:1 yeast iso-1 ferrocytochrome c/cytochrome c peroxidase compound I complex is essentially independent of ionic strength with a value of 3800 +/- 300 s-1. The Fe(IV) site in cytochrome c peroxidase compound I is preferentially reduced by yeast ferrocytochrome c between 0.01 and 0.20 M ionic strength while the Trp-191 radical is preferentially reduced above 0.30 M ionic strength. The association rate constant for the binding of yeast iso-1 ferrocytochrome c to cytochrome c peroxidase compound I can be evaluated and varies from a remarkable 1 x 10(10) M-1 s-1 at 0.01 M ionic strength to 1.2 x 10(5) M-1 s-1 at 1.0 M ionic strength. Between 0.01 and 0.20 M ionic strength, the reduction of cytochrome c peroxidase compound II to the native enzyme is anomalous. The reaction is independent of the cytochrome c concentration and directly proportional to the initial cytochrome c peroxidase compound I concentration.

UI	MeSH Term	Description	Entries
D007501	Iron	A metallic element with atomic symbol Fe, atomic number 26, and atomic weight 55.85. It is an essential constituent of HEMOGLOBINS; CYTOCHROMES; and IRON-BINDING PROTEINS. It plays a role in cellular redox reactions and in the transport of OXYGEN.	Iron-56,Iron 56
D007700	Kinetics	The rate dynamics in chemical or physical systems.
D008956	Models, Chemical	Theoretical representations that simulate the behavior or activity of chemical processes or phenomena; includes the use of mathematical equations, computers, and other electronic equipment.	Chemical Models,Chemical Model,Model, Chemical
D009994	Osmolar Concentration	The concentration of osmotically active particles in solution expressed in terms of osmoles of solute per liter of solution. Osmolality is expressed in terms of osmoles of solute per kilogram of solvent.	Ionic Strength,Osmolality,Osmolarity,Concentration, Osmolar,Concentrations, Osmolar,Ionic Strengths,Osmolalities,Osmolar Concentrations,Osmolarities,Strength, Ionic,Strengths, Ionic
D010084	Oxidation-Reduction	A chemical reaction in which an electron is transferred from one molecule to another. The electron-donating molecule is the reducing agent or reductant; the electron-accepting molecule is the oxidizing agent or oxidant. Reducing and oxidizing agents function as conjugate reductant-oxidant pairs or redox pairs (Lehninger, Principles of Biochemistry, 1982, p471).	Redox,Oxidation Reduction
D003574	Cytochrome c Group	A group of cytochromes with covalent thioether linkages between either or both of the vinyl side chains of protoheme and the protein. (Enzyme Nomenclature, 1992, p539)	Cytochromes Type c,Group, Cytochrome c,Type c, Cytochromes
D003578	Cytochrome-c Peroxidase	A hemeprotein which catalyzes the oxidation of ferrocytochrome c to ferricytochrome c in the presence of hydrogen peroxide. EC 1.11.1.5.	Cytochrome Peroxidase,Cytochrome c-551 Peroxidase,Cytochrome c 551 Peroxidase,Cytochrome c Peroxidase,Peroxidase, Cytochrome,Peroxidase, Cytochrome c-551,Peroxidase, Cytochrome-c
D005609	Free Radicals	Highly reactive molecules with an unsatisfied electron valence pair. Free radicals are produced in both normal and pathological processes. Free radicals include reactive oxygen and nitrogen species (RONS). They are proven or suspected agents of tissue damage in a wide variety of circumstances including radiation, damage from environment chemicals, and aging. Natural and pharmacological prevention of free radical damage is being actively investigated.	Free Radical
D001665	Binding Sites	The parts of a macromolecule that directly participate in its specific combination with another molecule.	Combining Site,Binding Site,Combining Sites,Site, Binding,Site, Combining,Sites, Binding,Sites, Combining
D012441	Saccharomyces cerevisiae	A species of the genus SACCHAROMYCES, family Saccharomycetaceae, order Saccharomycetales, known as "baker's" or "brewer's" yeast. The dried form is used as a dietary supplement.	Baker's Yeast,Brewer's Yeast,Candida robusta,S. cerevisiae,Saccharomyces capensis,Saccharomyces italicus,Saccharomyces oviformis,Saccharomyces uvarum var. melibiosus,Yeast, Baker's,Yeast, Brewer's,Baker Yeast,S cerevisiae,Baker's Yeasts,Yeast, Baker