SEPARATION AND PROPERTIES OF LOW-SPIN (HAEMOCHROME) AND NATIVE, HIGH-SPIN FORMS OF LEGHAEMOGLOBIN FROM SOYBEAN NODULE EXTRACTS

1. 1. About 95% of the ferroleghaemoglobin (Lb2+) in N2-fixing soybean root nodules is extracted and purified as autoxidized ferrileghaemoglobin (Lb3+) at pH 5.5. As the pH of extraction is raised less autoxidation occurs, at pH 7.9, 70 % more of the leghaemoglobin (Lb) is isolated as ferrous oxyleghaemoglobin (Lb2+O2). 2. 2. Although this Lb2+O2, when oxidized or deoxygenated, has the properties of a high-spin haemoprotein, autoxidized Lb3+, as present in crude extracts, is separable by chromatography on 'DEAE-Sephadex' in 13 mM sodium acetate (pH 5.2) into high-spin and low-spin (ferrihaemochrome)forms. 3. 3. This low-spin (ferrihaemochrome) form of Lb3+ probably arises by combination of autoxidized, high-spin Lb3+ with a low-molecular-weight ligand during extraction or initial purification. High-spin Lb2+ (or Lb2+O2) appears to be the natural, functional form of Lb. © 1969.