ABSTRACT
1. Human haptoglobin (Hp) type 2-1 was subjected to the sulfanilazo-modification of tyrosine and histidine residues, the removal of sialic acid, and the reduction of disulfide bonds (isolation of alpha 2, alpha 1, beta subunits), respectively. Radioactively labeled preparations were administered intravenously to rabbits. 2. Human Hp and isolated beta (heavy) chain disappeared from the circulation somewhat faster (half-lives = 72 and 67 h, respectively), than homologous rabbit Hp (half-life = 96 h). Hp light chains (alpha 2, alpha 1), devoid of oligosaccharide showed shorter half-lives of 27-19 h. 3. Treatment of Hp with diazotized sulfanilic acid resulted in an appreciable reduction of half-life to 21-11 h, as dependent on the number of modified residues. 4. Asialo-Hp, asialo-beta chain, and asialo-sulfanilazo-Hp were cleared rapidly from the circulation with half-lives of 5.5, 5.0, and 4.2 h, respectively. 5. These results suggest that in different pathways of Hp catabolism in vivo, polypeptide recognition markers in addition to carbohydrate ones, are involved.
Subject(s)
Haptoglobins/blood , Sulfanilamides/blood , Animals , Humans , Liver/metabolism , Rabbits , Sulfanilamides/pharmacokineticsABSTRACT
Secondary structure of alpha (light) and beta (heavy) chains of human haptoglobin was proposed. The Chou-Fasman predictive method was used in conjunction with the hydrophobic character and hydropathy scale value assigned to each amino acid residue in the primary sequence of the protein. Moreover, by means of hydrophilicity values of amino acids, the location of antigenic determinants was predicted.
