Oxygen equilibrium of hemoglobin Hiroshima

Direct measurement of the pK values of an alkaline Bohr group in human hemoglobin

Proton nuclear magnetic resonance spectra of normal and des-(his 146beta) human hemoglobin in the aromatic resonance region have been compared at different pH values. From these measurements, a pK value for histidine 146beta of 7.1 in carbonmonoxyhemoglobin and 8.0 in deoxyhemoglobin has been found. These pK values confirm the proposed role of histidine 146beta in the alkaline Bohr effect.

The interaction of 2,3-diphosphoglycerate with various human hemoglobins

Oxygen equilibria were measured on a number of human hemoglobins, which had been "stripped" of organic phosphates and isolated by column chromatography. In the presence of 2 x 10(-4) M 2,3-diphosphoglycerate (2,3-DPG), the P(50) of hemoglobins A, A(2), S, and C increased about twofold, signifying a substantial and equal decrease in oxygen affinity. Furthermore, hemoglobins Chesapeake and M(Milwaukee-1) which have intrinsically high and low oxygen affinities, respectively, also showed a twofold increase in P(50) in the presence of 2 x 10(-4) M 2,3-DPG. In comparison to these, hemoglobins A(IC) and F were less reactive with 2,3-DPG while hemoglobin F(I) showed virtually no reactivity. The N-terminal amino of each beta-chain of hemoglobin A(IC) is linked to a hexose. In hemoglobin F(I) the N-terminal amino of each gamma-chain is acetylated. These results suggest that the N-terminal amino groups of the non-alpha-chains are involved in the binding of 2,3-DPG to hemoglobin.