title: Dissociation and oxygen equilibrium properties of the extracellular hemoglobin of Eisenia foetida.
abstract: The dissociation and oxygen equilibrium properties of whole blood and the purified hemoglobin from Eisenia foetida were compared. Oxygen affinities agreed approximately with each other in the range of pH 6.0 to 9.5. The values of n1/2 were higher in whole blood than in the purified hemoglobin between pH 7.0 and 9.5. The maximum values, obtained near pH 8, were about 6 in whole blood and 3.5 in the purified hemoglobin. In the purified hemoglobin, alkaline dissociation started at pH 7.8, and the approximately 60 S whole molecule dissociated completely into approximately 10 S and 5-6 S components at pH 9.1. In whole blood, however, the dissociation started at pH 8.2 and the complete disappearance of the approximately 60 S molecule occurred at pH 9.6. The values of n1/2 for the dissociation products were lower than those of the purified hemoglobin between pH 7.0 and 9.0. The value of n1/2 decreased with increasing dissociation of the approximately 60 S whole molecule with a pH rise in both whole blood and the purified hemoglobin. Addition of CaCl2 or MgCl2 up to 10 mM to the purified hemoglobin at pH 8.0-8.1 induced increases in oxygen affinity and cooperativity and in the stability of the approximately 60 S whole molecule. The effect on the oxygenation properties was greater with CaCl2 than MgCl2 at the same molar concentration. The stabilizing effect on the approximately 60 S molecule was almost the same with both CaCl2 and MgCl2. These results suggest that the dissociation of property of the hemoglobin in whole blood is controlled by both Ca2+ and Mg2+, and that its oxygenation property is controlled by Ca2+.
mesh_terms: D000818:Animals; D002122:Calcium Chloride / Q000494:pharmacology; D055598:Chemical Phenomena; D002621:Chemistry; D006454:Hemoglobins / Q000032:analysis*; D006863:Hydrogen-Ion Concentration; D008274:Magnesium / Q000494:pharmacology; D015636:Magnesium Chloride; D009835:Oligochaeta / Q000378:metabolism*; D010100:Oxygen / Q000097:blood
chemical_list: D006454:Hemoglobins; D015636:Magnesium Chloride; D008274:Magnesium; D002122:Calcium Chloride; D010100:Oxygen