ON THE EVOLUTION OF HEMOGLOBIN. RESPIRATORY PROPERTIES OF THE HEMOGLOBIN OF THE CALIFORNIA HAGFISH, POLISTOTREMA STOUTI

Abstract

1. Oxygen equilibria of hagfish hemoglobin inside and outside the red blood cell have been obtained under a variety of conditions. The oxygen affinity of the hemoglobin in the erythrocyte suspensions is high (p50 = 3-4 mm. Hg at 18°), although it is even higher in hemoglobin solutions (p50 = 1.8 mm. Hg at 18° C.). There is no interaction between hemes (n = 1.00) and virtually no Bohr effect. The effect of temperature on the oxygen equilibrium of hagfish hemoglobin is similar to that observed in recent experiments on other hemoglobins (ΔH° = - 9.3 kcal. for hagfish hemoglobin).2. Several aspects of Wald's (1952; see, also, Wald and Allen, 1957) theories on the evolution and function of hemoglobin are criticized in view of these data on hagfish hemoglobin and on the basis of information in the literature. It is concluded that: (1) At present there is no reason to favor cytochrome oxidase as the phylogenetic precursor of hemoglobin. (2) Many invertebrate hemoglobins function in oxygen transport. (3) If the internal oxygen tensions are sufficiently low, a respiratory pigment participating in oxygen transport does not need to possess a low oxygen affinity, a sigmoid oxygen dissociation curve, and a marked Bohr effect. (4) It is impossible to say if a particular set of properties of the oxygen equilibrium is basically "primitive." (5) Physiological conclusions on hemoglobin should be made upon studies of the pigment in the natural condition—i.e., myoglobin in the muscle, or intracellular vascular hemoglobin in the erythrocyte.