Functional Properties of Hemoglobins

Abstract

Some hemoglobins change in degree of aggregation when oxygenated. This is one possible explanation for "heme-heme interaction". In lamprey and bullfrog hemoglobulins the pH dependence (Bohr effect) of the O2 equilibrium decreases greatly as the protein concentration decreases. This occurs in human and turtle hemoglobins, although the effect is smaller and occurs at lower concentrations. Oxygenation of certain red cells pass through capillaries. The effects of such changes on the ionic environ-ment of hemoglobin and on the O2 equilibirum are only partly known for a few hemoglobins. Attempts to associate specific properties of hemoglobin with the physiology of an organism may be difficult for those invertebrate animals in which the hemoglobin is only margin-ally important. The functions of hemoglobin are obscure among microorganisms. Hemoglobin within thin films can faciltate gas transport across the film. This function is probably important for myoglobin in muscle, and perhaps such a function can be attributed to the hemoglobins reported from protozoa, yeast, Penicillium, and Neurospora. The function of hemoglobin in root nodules of leguminous plants is uncertain. The primary function of root nodule hemoglobin may be to bind N.