Kinetics of the reaction with oxygen of mixtures of oxy- and carbon monoxide hemoglobin.

نویسندگان

  • M Brunori
  • E Antonini
چکیده

The paper reports rapid mixing and relaxation experiments performed on mixtures of oxy(HbOz) and carbon monoxide (HbCO) human hemoglobin. On the (well justified) assumption that the two ligands will distribute at random between the available sites, intermediates containing different proportions of 02 and CO will be formed. In the stopped flow experiments mixtures containing different proportions of the two ligands have been mixed with sodium dithionite (Na2S?O& which rapidly reduces to zero the O2 concentration in the system. The apparent dissociation velocity constant for 0, (k,rf) measured under these conditions decreases progressively as the fraction of HbCO in the mixture increases, in agreement with previous observations on sheep hemoglobin. Temperature jump experiments performed on mixtures of HbCO and HbOg show that the amplitude of the faster relaxation time (TV) relative to that of the slower one (TV) increases as the percentage of HbCO in the mixture is progressively increased. At high enough percentage of HbCO (>i’O%), the amplitude of the faster relaxation time becomes dominant. The reciprocal relaxation time (~~-l), measured under these conditions, is linearly dependent on oxygen concentration, while it is independent of protein concentration (so long as O2 is buffered). The apparent second order velocity constant is k,, = 4.8 X lo7 M-I s-l at 25”. Simple considerations indicate that the kinetics of the reaction with oxygen of mixtures containing high enough percentages of HbCO should represent the combination and dissociation velocity constants of high affinity forms of hemoglobin.

برای دانلود رایگان متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید

ثبت نام

اگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید

منابع مشابه

The effect of inositol hexaphosphate on the kinetics of CO and O 2 binding by human hemoglobin.

The binding of inositol hexaphosphate (IHP) to oxyhemoglobin (oxy-Hb) was investigated by gel filtration and stopped flow kinetic methods. The stoichiometry of the complex is 1 IHP per hemoglobin tetramer in 0.05 M Z,Z-bis(hydroxymethyl)-2,2’,2”nitrilotriethanol (pH 7.0) containing 0.11 M NaCl and appears to approach 2 IHP per tetramer when the ionic strength is reduced to 0.01. The dissociatio...

متن کامل

The Role of Aldehydes as Degenerate Branching Intermediate in the Oxidation of Hydrocarbons

The thermal oxidation of propane in the temperature range 350-425oC was studied in order to elucidate the role of higher aldehydes as degenerate branching intermediates in the oxidation of hydrocarbons. In the slow combustion of propane, the high yield of propylene and methanol as the primary products, the formation of hydrogen peroxide, carbon monoxide, carbon dioxide, formaldehyde and steam a...

متن کامل

The Kinetics of Methanation on Nickel Catalysts

An empirical rate equation was obtained for the methanation kinetics catalyzed by MCR-2X, a commercial catalyst prepared by Haldor-Topsoe. The studies were carried out in a fixed-bed reactor under differential conditions, and in a gradientless recycle reactor (Berry) over a range of total pressures, reactant concentractions (H2/CO ratios), and temperatures. The kinetics of methanation were foun...

متن کامل

A tri state mechanism for oxygen release in fish hemoglobin: Using Barbus sharpeyi as a model

Hemoglobin is a porphyrin containing protein with an a2b2 tetrameric structure and like other porphyrin compounds shows spectral behavior of species specific characteristics. Researchers tend to relate bands in the hemoglobin spectra to certain structural and/or functional features. Given the fact that hemoglobin is the main oxygen carrier in animals functioning through the Oxy«Deoxy equilibriu...

متن کامل

Kinetics of oxygen and carbon monoxide binding to liver fluke (Dicrocoelium dendriticum) hemoglobin. An extreme case?

The kinetics of oxygen and carbon monoxide binding to the monomeric liver fluke (Dicrocoelium dendriticum) hemoglobin have been studied. The ligand association rates are approximately 1 X 10(8) and approximately 3 X 10(8) M-1 s-1, respectively, for CO and O2 and show no pH dependence. On the contrary the ligand dissociation rates decrease by lowering the pH below 7, the pK of the transition bei...

متن کامل

ذخیره در منابع من


  با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید

عنوان ژورنال:
  • The Journal of biological chemistry

دوره 247 13  شماره 

صفحات  -

تاریخ انتشار 1972