Effect of anions on the oxygen binding properties of the hemoglobin components from trout (Salmo irideus).

The effect of several anions on the oxygen equilibrium of hemoglobin components (Hb Trout I, II, and IV) from trout has been investigated.The functional properties of Hb Trout I and II are very slightly affected by organic phosphates (ATP, IHP) and pyridoxal phosphate. On the other hand the oxygen affinity of both components is affected, to the same extent, by the presence of sodium chloride; this effect seems to be pH and temperature independent. For Hb Trout I experiments on the effect of orthophosphate, pyrophosphate and pyridoxal phosphate point to a certain degree of correlation between the size of the phosphate and its effect on the functional behavior of the protein.In the case of Hb Trout I and II the differences in the effect of the various organic and inorganic phosphates may be interpreted, at a molecular level, in terms of loss of charge complementarity and (or) steric hindrance effects.On the other hand, as in the case of human hemoglobin, organic or inorganic phosphates decrease the oxygen affinity of Hb Trout IV. In addition various phosphates shift the region where the Root effect is operative toward higher pH values, thereby acting as allosteric effectors. For pyridoxal phosphate, kinetic experiments have shown that the rate of binding to Hb trout IV is several orders of magnitude smaller than that for other organic phosphates, similarly to what has been reported for human hemoglobin.