STUDIES ON PROPERTIES OF FISH HEMOGLOBINS - KINETICS OF REACTION WITH OXYGEN AND CARBON-MONOXIDE OF ISOLATED HEMOGLOBIN COMPONENTS FROM TROUT (SALMO-IRIDEUS)

The ligand-binding kinetics of the isolated component from trout (Salmo irideus) blood has been extensively investigated; it appears to be fully consistent with their equilibrium behaviour, described previously. At alkaline pH (∼ 7.5), in a region where the Root effect is not operative, comparison of the kinetics of the various components (Hb trout I, II and IV) shows considerable similarities between them. For Hb trout I (and II) the time course of the reaction with both O2 and CO is practically pH independent. On the other hand Hb trout IV, characterized by a Root effect, displays a strong dependence on pH of the kinetics of ligand binding. Thus in the pH region where the Root effect becomes operative there is a large change of the character, as well as of the speed, of the kinetics with both O2 and CO. The Root effect characteristic of Hb trout IV appears to originate, from a kinetic point of view, in a pH-dependent change of both the “on” and “off” constants, although at least for O2 the effect of pH on the “off” kinetic constants is much more marked.