STUDIES ON FUNCTIONAL PROPERTIES OF FISH HEMOGLOBINS .2. OXYGEN EQUILIBRIUM OF ISOLATED HEMOGLOBIN COMPONENTS FROM TROUT BLOOD

Homogeneous components of trout hemoglobin (Salmo irideus) have been isolated by column chromatography. The oxygen equilibrium of the two main components has been investigated. The oxygen affinity and the shape of the ligand equilibrium curve is independent of pH for component I. On the other hand, component IV is characterized by a very large Bohr effect, to which a considerable change in the shape of the oxygen equilibrium curve with pH is associated. The different oxygen-binding behavior of the isolated components can explain data obtained with the whole blood and in particular the contribution of the various proteins to the Root effect. The dependence on pH of the apparent ΔH for oxygenation has been measured for both components. Component I is characterized by a fairly low (ΔH ~ −3 kcal/mole) and pH independent value of the enthalpy change, while for component IV the apparent ΔH decreases from ~ −14 kcal/mole at pH near 9 to ~ −7 kcal/mole at pH 7.