Biomaterial Database

Biphasic nature in the autoxidation reaction of human oxyhemoglobin. 1997

M Tsuruga, and K Shikama

Biological Institute, Graduate School of Science, Tohoku University, Sendai, Japan.

In comparison with myoglobin molecule as a reference, we have studied the autoxidation rate of human oxyhemoglobin (HbO2) as a function of its concentration in 0.1 M buffer at 35 degrees C and in the presence of 1 mM EDTA. At pH 6.5, HbA showed a biphasic autoxidation reaction that can be described completely by a first-order rate equation containing two rate constants-kf, for fast autoxidation of the alpha-chain, and ks, for slow autoxidation of the beta-chain, respectively. When tetrameric HbO2 was dissociated into alpha beta-dimers by dilution, the value of kf increased markedly to an extent comparable with the autoxidation rate of horse heart oxymyoglobin (MbO2). The rate constant Ks, on the other hand, was found to remain at an almost constant value over the whole concentration range from 1.0 x 10(-3) M to 3.2 x 10(-6) M in heme. At pH 8.5 and pH 10.0, however, the autoxidation of HbO2 was monophasic, and no enhancement in the rate was observed by diluting hemoglobin solutions. Taking into consideration the effects of 2,3-diphosphoglyceric acid and chloride anion on the autoxidation rate of HbO2, we have characterized the differential susceptibility of the alpha- and beta-chains to the autoxidation reaction in aqueous solution.

UI	MeSH Term	Description	Entries
D007700	Kinetics	The rate dynamics in chemical or physical systems.
D008706	Methemoglobin		Ferrihemoglobin
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
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
D010108	Oxyhemoglobins	A compound formed by the combination of hemoglobin and oxygen. It is a complex in which the oxygen is bound directly to the iron without causing a change from the ferrous to the ferric state.	Oxycobalt Hemoglobin,Oxycobalthemoglobin,Oxyhemoglobin,Hemoglobin, Oxycobalt
D011189	Potassium Chloride	A white crystal or crystalline powder used in BUFFERS; FERTILIZERS; and EXPLOSIVES. It can be used to replenish ELECTROLYTES and restore WATER-ELECTROLYTE BALANCE in treating HYPOKALEMIA.	Slow-K,Chloride, Potassium
D011487	Protein Conformation	The characteristic 3-dimensional shape of a protein, including the secondary, supersecondary (motifs), tertiary (domains) and quaternary structure of the peptide chain. PROTEIN STRUCTURE, QUATERNARY describes the conformation assumed by multimeric proteins (aggregates of more than one polypeptide chain).	Conformation, Protein,Conformations, Protein,Protein Conformations
D003198	Computer Simulation	Computer-based representation of physical systems and phenomena such as chemical processes.	Computational Modeling,Computational Modelling,Computer Models,In silico Modeling,In silico Models,In silico Simulation,Models, Computer,Computerized Models,Computer Model,Computer Simulations,Computerized Model,In silico Model,Model, Computer,Model, Computerized,Model, In silico,Modeling, Computational,Modeling, In silico,Modelling, Computational,Simulation, Computer,Simulation, In silico,Simulations, Computer
D004163	Diphosphoglyceric Acids	Glyceric acids where two of the hydroxyl groups have been replaced by phosphates.	Bisphosphoglycerates,Acids, Diphosphoglyceric
D006801	Humans	Members of the species Homo sapiens.	Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man