Functional studies on the separated hemoglobin components of an air-breathing catfish, Hoplosternum littorale (Hancock)

1. 1. The two hemoglobins, Hb I and II, of the obligate air-breathing catfish, Hoplosternum littorale have been isolated. 2. 2. The unfractionated stripped hemoglobin has a high oxygen affinity, a normal alkaline Bohr effect, and a Root effect. 3. 3. Both the Bohr and Root effects are enhanced by 1 mM ATP. 4. 4. Stripped Hb I has a relatively high oxygen affinity, a reversed Bohr effect between pH 6.0 and 8.0 ( Δlog P₅₀ †DpH > 0), but no Root effect. Addition of 1 mM ATP to Hb I causes a marked reduction in the oxygen affinity, a change to a normal alkaline Bohr effect ( Δlog P₅₀ ΔpH < 0), but no Root effect. 5. 5. Stripped Hb II has a lower oxygen affinity at low pH and a higher oxygen affinity at high pH than does Hb I. Hb II shows a large alkaline Bohr effect which is only slightly increased by 1 mM ATP and a Root effect at low pH which is enhanced by 1 mM ATP. 6. 6. The observed rates of O₂ dissociation and of CO combination with Hbs I and II show differences which parallel those observed in the oxygen equilibrium measurements.