Comparative physiological studies of regulation mechanism of hemoglobin function

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By comparing oxygen binding properties of hemoglobins of various animals, we intended to get insight into the molecular mechanisms that are unique for each hemoglobin or common to all of them, and finally, structure-function relationships in human adult hemoglobin.1. To examine the hypothesis that <alpha>89 His makes a great contribution to the alkaline Bohr effect of human adult hemoglobin, we measured the Bohr effect of canine hemoglobin in which His at <alpha>89 site is replaced by Tyr residue. The result did not support the hypothesis.2. Oxygen equilibrium curves for red cells and hemoglobins from four amphibian species: Onychodactylus japonicus, Megalobatrachus sligoi, Andrius japonicus, and Cryptobranchus alleganiensis were determined under a variety of experimental conditions and compared with each other or with those of human hemoglobin. The salamander hemoglobins showed lowered oxygen affinity and very small Bohr effect compared to those of human hemoglobin. Moreover, the salamander hemoglobins showed little heterotropic effects caused by C1^1, Ca^<2+>, CO_2, ATP, IHP and inorganic phosphate.3, To test a possible Root effect of hemoglobin from Xenopus laevis, its oxygen eauilibrium curves were measured at a wide pH range. Although the Hill coefficient became smaller as pH was decreased, no conclusive data on the Root effect was not obtained because of repid autoxidation.