Separation and characterization of Menhaden hemoglobin components.

Hemolysate from Brevoortia tyrannus (Atlantic Menhaden) consists of two major and two minor components, as determined by ion-exchange chromatography. Oxygen equilibria, flash photolysis and rapid mixing techniques are used to detect functional differences between the two major components, revealing a system analogous to the Trout I-IV system. Menhaden IV exhibits a moderate Root effect and is sensitive to organic phosphate inhibition. Menhaden I exhibits little sensitivity to pH changes or the presence of organic phosphates. These differences are probably based on contrasting kinetic behavior, subunit heterogeneity and replacement of a COOH-terminal histidine residue. Theories accounting for the significance of functional hemoglobin multiplicity are reviewed. By bypassing the normal physiological unloading mechanisms, Menhaden I may be functioning as an oxygen reservoir, perhaps for red muscle during periods of high activity.