Studies of the functional properties of the hemoglobins of Hoplias malabaricus and Hoplerythrinus unitaeniatus

1. 1. Hemolysates from Hoplias malabaricus and Hoplerythrinus unitaeniatus show blurred hemoglobin patterns with three and four bands, respectively, by alkaline disc gel electrophoresis. 2. 2. The oxygen affinity of the stripped hemoglobin from Hoplerythrinus is about a third of that from Hoplias; the P₅₀ value of Hoplias Hb is about 1.3 mm Hg (pH 6.9 and 20°C). The addition of 1 mM ATP lowers the oxygen affinity of each hemoglobin 2.6-fold. 3. 3. Both hemoglobins show Root and Bohr effects; Δlog P₅₀ ΔpH = -0.40 for a stripped hemoglobins for the interval pH 7-8. 4. 4. The rate of dissociation of oxygen from each hemoglobin is similar and is kinetically homogeneous with rate constants decreasing from 200-250/sec at pH 6.2 to about 25-26 at pH 7.7 with or without 1 mM ATP. 5. 5. The CO combination reaction for Hoplias hemoglobin is kinetically heterogeneous at all pH values and for Hoplerythrinus hemoglobin below pH 7.5. The fast and slow phases each account for about half the observed reaction. The kinetic heterogeneity is maximal at low pH for both hemoglobins. The fast phase for Hoplias hemoglobin is more than twice as fast as that for Hoplerythrinus hemoglobins.