The root effect hemoglobin of the jaraqui´, a teleost fish,Prochilodus sp.

Abstract

1. The hemoglobin system of the jaraqui´,Prochilodus sp., consists of multiple hemoglobin components.2. The oxidized derivative elutes as a single molecular weight species in gel filtration experiments. The car☐y derivative has an apparent molecular weight of 60,000 as determined by gel filtration.3. A 44-fold change inp1/2 occurs between pH 6.4 and 8.6 in stripped hemoglobin solutions. This change increases to 388-fold over the same pH range in the presence of 1 mM ATP.4. Cooperativity in oxygen binding, as measured byn in the Hill equation, is greater than one at pH values above 6.7 but less than one below this value.5. The hemolysate displays a Root effect, being only 44% saturated at pH 6.4 in the presence of 1 mM ATP and equilibrated with air at 1 atm.6. At 30° C and pH 7.6 the whole blood possesses a lowp1/2, 4.7 mm Hg, lower than that of many other Amazonian teleosts.7. Both the carbon monoxide combination rate and the oxygen dissociation rate are pH and ATP dependent. Between pH 6.2 and 8.8 the COon rate increases 10-fold. ATP reduces the rate at intermediate pH values. The O2off rate increases 2.4-fold between pH 8.8 and 6.7. Addition of 1 mM ATP causes a 4.5-fold increase over the same pH range.8. The lown values below pH 6.7 and the heterogeneity of the CO combination and O2 dissociation processes suggests that the hemoglobin components may be functionally differentiated and/or intramolecular differences exist in the kinetic properties of α- and β-like chains.