The reactive unit of hemoglobin in hemoglobin-haptoglobin complex formation

Enzymic N-demethylation reaction catalysed by red blood cell cytosol

Red blood cell cytosol promotes enzymic N-demethylation reactions which display typical Michaelis-Menten kinetics with respect to N-methylaniline as substrate. The demethylase activity is linked with hemoglobin (Hb) and is enhanced in the presence of NADH and the NADH-methemoglobin reductase system. It has been adduced that Hb in its oxygenated form is involved in the reaction.

A general affinity chromatographic method for preparing monospecific antibody to mammalian serum haptoglobin

A general affinity chromatographic method for preparation of monospecific antibody to serum haptoglobin of any species is described. Hemoglobin prepared from the species to be immunized is coupled to an organomercurical substituted agarose gel support (Affi-Gel 501). The immobilized hemoglobin binds haptoglobin with great affinity and allows removal of other serum proteins by extensive washing. The haptoglobin-hemoglobin complexes are then specifically eluted by buffers containing dithiothreitol or other thiols and are further purified by chromatography on concanavalin A-agarose and Sephacryl S-200 columns. The pure complexes are very effective immunogens. Potent monospecific antisera to rabbit and to human haptoglobin have been prepared. The potential usefulness of affinity chromatography support media with specifically cleavable ligand sites in studies of haptoglobin and in other biological studies is discussed.

Studies on the binding of haemoglobin by haptoglobin using electrofocusing and gradient electrophoresis

1. Gel electrofocusing followed by gel gradient electrophoresis separated the haptoglobins and their complexes with haemoglobin into characteristic two-dimensional patterns of protein bands. 2. Molecular weights of 107 000, 139 000 and 168 000 were obtained for the three bands seen after a purified preparation of haptoglobin type 1 was partially saturated with haemoglobin. This indicated that free haptoglobin, the intermediate haptoglobin-haemoglobin complex containing one half-haemoglobin and the saturated complex with two half-haemoglobins were present. 3. The three proteins showed considerable microheterogeneity and gave a number of isoelectric points in the pH ranges 4.58-4.77, 5.20-5.40 and 5.74-5.93, free haptoglobin type 1 being the lowest group. These ranges were all 0.15-0.30pH units lower if other values were taken for the isoelectric points of markers used to calibrate the pH gradient. 4. All three proteins were present over a wide range of haemoglobin concentrations, from 0.5% to 92% of that required for saturation. This would be expected if both binding sites have similar affinities for haemoglobin.