A three-state MWC analysis of oxygenation in tench (Tinca tinca) hemoglobin
| Autor: | Jørgen Boiden Pedersen, Frank B. Jensen, Lars Garby |
|---|---|
| Rok vydání: | 1990 |
| Předmět: |
Physiology
Chemistry Allosteric regulation Enthalpy Mineralogy Thermodynamics chemistry.chemical_element Human physiology Oxygenation Biochemistry Oxygen chemistry.chemical_compound Endocrinology Organic phosphates Nucleoside triphosphate Animal Science and Zoology Hemoglobin Ecology Evolution Behavior and Systematics |
| Zdroj: | Journal of Comparative Physiology B. 160:407-411 |
| ISSN: | 1432-136X 0174-1578 |
| DOI: | 10.1007/bf01075672 |
| Popis: | Oxygen equilibria in tench hemoglobin were analysed according to a three-state MWC model. In addition to theT andR states of the traditionally used two-state model, the three-state model introduces an additional state, theS state, when organic phosphates bind to theT-structure hemoglobin. Under conditions covering natural red cell pH values and nucleoside triphosphate-hemoglobin ratios, it was possible to closely fit experimental data to the three-state equation with constant values of the association constantsKR,KT, andKS, and with only the allosteric constantsL andM varying with effector conditions. Thus, in contrast to a twostate analysis of oxygen equilibria, the three-state analysis was consistent with the basic assumption of the MWC model, that heterotropic ligands only affect allosteric constants and not association constants. The temperature-dependence of the three-state parameter values showed that in the presence of nucleoside triphosphate the dominance of theS state over theT state was most pronounced at low temperatures. Furthermore, the numerical values of the enthalpy and entropy change of oxygenation were lower in theS state than in theT andR states, and the enthalpy and entropy change for the allostericS→R transition were much larger than for theT→R transition. |
| Databáze: | OpenAIRE |
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