ABSTRACT
Plasma haptoglobin (Hp) is a genetically determined α2-acidic glycoprotein which combines specifically with hemoglobin, showing an activity of the “true” peroxidase type. Despite years of investigations, the physiological functions of haptoglobin have remained enigmatic. Analysis of human genomic clones led to the isolation of an haptoglobin-related protein sequence and to a demonstration of its structural homology to the Hp gene. Catabolic experiments with haptoglobin have been carried out by administration of radioactively labeled haptoglobin preparations to humans, dogs, rabbits, chickens, etc. A specific receptor for asialohaptoglobin in the liver was identified and characterized. Profound changes in serum haptoglobin level occur in a great variety of disease states. The occurrence of polymorphism at the haptoglobin locus has motivated many investigations directed at the determination of possible associations between haptoglobin phenotype distribution and different disorders. The molecular basis of the complex formation of haptoglobin with these ligands has been investigated by means of various modifications of the haptoglobin structure.
