La biologie des hématinoprotéides oxygénables

The author reviews a series of biological aspects of the study of oxygenable hematinoproteids, particularly with respect to evolution and adaptation. After a statement of some fundamental concepts of comparative biochemistry and of possible evolutionary relations between oxidation catalysts and oxygen carriers, the natural distribution of hemoglobins is reviewed and their specific characters are enumerated. A review is made of the data relating to the shape of the oxygen-dissociation curves and to the affinity of haemoglobin for oxygen. It appears, generally speaking, that hyperbolic or almost hyperbolic curves and high affinity for oxygen are characteristic of primitive or embryonic haemoglobins. A study of the function of haemoglobin in the respiratory cycle of several animal species shows the vital importance of the oxygen carrier as well as the adaptation of the shape and position of the dissociation curve to the character of the respiratory function in the animal considered. The function of haemoglobin in invertebrates, as oxygen carrier as well as providing a store of oxygen, is emphasized by a review of experimental data. The function of oxygen in the transport of carbon dioxide is reviewed from the standpoint of comparative biochemistry, and the lack of our knowledge is deplored. The characteristics of chlorocruorin show it to be a chemical mutation of an Annelid haemoglobin. Our lack of knowledge in the field of the comparative biochemistry of haemoglobin and chlorocruorin metabolism is pointed out.