Estudo das propriedades funcionais da hemoglobina de Hoplias malabaricus e Hoplerythrinus unitaeniatus ^*

Summary

Hemolysates from Hoplias malabaricus and Hoplerythrinus unitaeniatus show blurred hemoglobin patterns with 3 and 4 bands, respectively, by alkaline disc gel electrophoresis. The oxygen affinity of the stripped hemoglobin from Hoplerythrinus is about a third of that from Hoplias; the P₅₀ value for 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. Both hemoglobins show Root and Bohr effects; Δ log P₅₀/Δ pH = — 0.40 for the stripped hemoglobins for the interval pH 7-8. The rate of dissociation of oxygen from each hemoglobin is similar and is kinetically homogeneous with rate constants decreasing from 200-250 sec^-1 at pH 6.2 to about 25-26 at pH 7.7 with or without 1 mM ATP. 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 that for Hoplerythrinus hemoglobins.