Evidence of homology between the β-chain of human haptoglobin and the chymotrypsin family of serine proteases

Alexander Kurosky, Don R. Barnett, Marily A. Rasco, Tong Ho Lee, Barbara H. Bowman

Research output: Contribution to journalArticlepeer-review

18 Scopus citations


Amino acid sequences from the β-chain of human haptoglobin are compared with those sequences known for the serine proteases of the chymotrypsin family. In a comparison of some 171 residues of the haptoglobin β-chain (approximately 60% of the protein molecule), approximately 30% of these are identical to residues occurring in sequences of either bovine trypsin, bovine chymotrypsin A, bovine chymotrypsin B, porcine elastase, or bovine thrombin B-chain, and an additional 10% are chemically similar. A combined comparison of the haptoglobin β-chain with the above five serine proteases gave an identity of 56% and a chemical similarity of 11%. Similarity of primary structure is also striking around two of the five half-cystinyl residues so far characterized in long lengths of sequence. These data provide substantial evidence that the β-chain of haptoglobin is homologous to the chymotrypsin family of serine proteases. Proposals are also presented to explain the occurrence of internal homology in the N-terminal region of the β-chain.

Original languageEnglish (US)
Pages (from-to)279-293
Number of pages15
JournalBiochemical Genetics
Issue number4
StatePublished - Apr 1974
Externally publishedYes


  • amino acid sequences
  • chymotrypsin
  • elastase
  • haptoglobin
  • plasmin
  • protein homology
  • serine proteases
  • thrombin
  • trypsin

ASJC Scopus subject areas

  • Genetics
  • Ecology, Evolution, Behavior and Systematics
  • Molecular Biology
  • Biochemistry


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