Recent New Characterizations on the Giant Extracellular Hemoglobin of Glossoscolex paulistus and Some Other Giant Hemoglobins from Different Worms

Abstract

Giant extracellular hemoglobins, also known as erythrocruorins, have been investigated as a model of extreme complexity in oxygen-binding heme proteins [1,2]. They are characterized by a very high molecular mass (MM) of several megadalton (MDa), and their oligomeric structure together with the crowded and protected heme environment are two of the main factors responsible for the high redox stability [3,4]. Superoxide dimustase (SOD)-like intrinsic activity, observed for hemoglobins of Lumbricus terrestris (HbLt) and of Arenicola marina (HbAm), is another important factor [5,6]. These hemoglobins present a highly cooperative oxygen binding and a peculiar behavior associated to their oligomeric dissociation into smaller subunits and possible rearrangement back into the native oligomeric structure [7,8].