Amino acid sequence of serine protease inhibitor CI-1 from barley. Homology with barley inhibitor CI-2, potato inhibitor I, and leech eglin

  • IB Svendsen
  • Sigurd Boisen
  • Jørn Hejgaard


Three molecular forms of a protein inhibitor of chymotrypsin and microbial alkaline proteases have been isolated from Hiproly high-lysine barley.

Automated Edman degradation of one of these inhibitor preparations (CI-1C) resulted in the following amino acid sequence (77 residues in total): Tyr-Pro-Glu-Pro-Thr-Glu-Gly-Ser-Ile-Gly-Ala-Ser-Gly-Ala-Lys-Thr-Ser-Trp-Pro-Glu-Val-Val-Gly-Met-Ser-Ala-Glu-Lys-Ala-Lys-Glu-Ile-Ile-Leu-Arg-Asp-Lys-Pro-Asn-Ala-Gln-Ile-Glu-Val-Ile-Pro-Val-Asp-Ala-Met-Val-Pro-Leu-Asn-Phe-Asn-Pro-Asn-Arg-Val-Phe-Val-Leu-Val (His, Lys, Ala, Thr, Thr, Val, Ala, Glx, Val, Ser, Arg) Val-Gly.

The inhibitor (CI-1) is homologous with another barley inhibitor (CI-2), with potato inhibitor I and with the elastase-cathepsin G inhibitor eglin from the leech Hirudo medicinalis (30–50% of the amino acid residues in identical positions). This established «family of cystine-independent inhibitors» also showed some sequence similarities with the cystine-free yeast proteinase B inhibitors 1 and 2. In the reactive site region homologies with the cystine-rich inhibitors of the «Kazal pancreas secretory inhibitor» and the «Streptomyces subtilisin inhibitor» families were observed.


Hiproly barley chymotrypsin inhibitor subtilisin inhibitor 




CI-1 and CI-2

chymotrypsin inhibitor 1 and 2 from barley (3)


Leech inhibitor eglin (17)


potato inhibitor I (15)


hexadimethrine bromide




sodium dodecyl sulfate


N,N,N′,N′,-tetrakis (2-hydroxyethyl)ethylenediamine


yeast inhibitor of protease B (11)


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Copyright information

© Carlsberg Laboratory 1982

Authors and Affiliations

  • IB Svendsen
    • 1
  • Sigurd Boisen
    • 2
  • Jørn Hejgaard
    • 2
  1. 1.Department of ChemistryCarlsberg LaboratoryCopenhagen Valby
  2. 2.Department of Biochemistry and NutritionTechnical University of DenmarkLyngby

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