The Biological Significance of Haemoglobin in Nematode Parasites I. The Characteristics of the Purified Pigments

Abstract

Haemoglobins from Nippostrongylus muris, Nematodirus·spp., and Haemonchus contortus were purified by ammonium sulphate fractionation and their properties examined. All the haemoglobins showed a very high affinity for oxygen; the tension of half saturation (P50) for Nematodirus haemoglobin of concentrations about 1 x 10-4 g.-atoms of iron per 1. at pH 7.4 was in the region of 0.04 mm. of mercury. The P50 for H. contortus haemoglobin was similar to that of Nematodirus .spp.; N. muris haemoglobin had a somewhat higher p:;o' The. parasite haemoglobins all showed an unusually low affinity for carbon monoxide, the equilibrium constant, K = [HbCO] X p02/[Hb02] X pCO, having a value of about 1. The "span," the distance between the a-bands of oxyhaemoglobin and carboxyhaemoglobin, varied from 60 to 65 A. for the three parasites. None of the haemoglobins obtained from the parasites showed properties supporting the view that there is a linear relationship between log K and the "span."