RESUMO
The water-snake Liophis miliaris presentes hemoglobin which binds organic polyphosphate through a simple single-site per tetramer (Mol. Wt. 64500) as judged by titration curves of reduced nicotinamide adenine dinucleotide phosphate either in the presence or absence of inositol hexaphosphate. The site seems to have the same structural nature of that found on other hemoglobins and is able to strongly bind most of the known protein effectors such as inositol hexaphosphate, adenosine triphosphate or 2,3-disphosphoglicerate. The high association constant at pØ7 of reduced nicotinamide for the deoxy hemoglobin of about K (D) = 7 x 10***6 M***-1 comparaed to human hemoglobin (K(D) = 7 x 10***5 M***-1), and to that of adenosine triphosphate (its natural erythrocytic polyphosphate) still higher of about K(D) = 10***11 M ***-1, shows clearly the very high affinity of this snake hemoglobin for such allosteric effector. The results besides corroborating the dimer-tetramer transition mechanism proposed to describe the oxygen transport by the hemoglobin of Liophis miliaris - may explain the difficulties to obtain the oxy dimeric conformation of the protein by usual hemolysis and stripped off procedures