Oxygen Binding and Stability Properties of Hb Santa Ana (β88 Leu→Pro)

Abstract

Hb Santa Ana (β88 Leu→Pro) was found at a level of 30% of total hemoglobin in red cells from a patient with congenital hemolytic anemia. Since no detailed functional studies of this hemoglobin have been done previously, we determined oxygen equilibrium curves of red cell suspensions, hemolysates, and isolated Hb Santa Ana. The P₅₀ values obtained were 22.5 mm Hg (37°C, pH 7.4) for red cell suspensions (normal mean = 27.0 mm Hg), 10.0 mm Hg (25°C, pH 7.0) for hemolysate (normal = 13.5 mm Hg), and 1.3 mm Hg (25°C, pH 7.0) for isolated Hb Santa Ana. Measurements of mechanical stability of Hb Santa Ana showed that the oxy-form of this hemoglobin was 10 times more unstable than that of Hb S and 100 times more unstable than that of Hb A. The deoxy-form of Hb Santa Ana was as unstable as its oxy-form, indicating that no stabilization (R→T conversion) takes place upon the deoxygenation of Hb Santa Ana.