PROSITE documentation PDOC00252
Pancreatic trypsin inhibitor (Kunitz) family signature and profile


The pancreatic trypsin inhibitor (Kunitz) family [1,2,3] is one of the numerous families of serine proteinase inhibitors. The basic structure of such a type of inhibitor is shown in the following schematic representation:

            |  +--------+           |
            |  |      **|*******    |
                    |          |

            <------50 residues------>
'C': conserved cysteine involved in a disulfide bond.
'#': active site residue.
'*': position of the pattern.

In addition to the prototype sequence for this type of inhibitor - the bovine pancreatic trypsin inhibitor (BPTI) (also known as basic protease inhibitor (BPI)) - this family also includes many other members which are listed below (references are only provided for recently determined sequences):

  • Mammalian inter-α-trypsin inhibitors (ITI). ITI's contain two inhibitory domains.
  • Tissue factor pathway inhibitor precursor (TFPI) (previously known as lipoprotein-associated coagulation inhibitor (LACI)), which inhibits factor X (Xa) directly and, in a Xa-dependent way, inhibits VIIa / Tissue factor activity. TFPI contains three inhibitory domains.
  • TFPI-2 [4] (also known as placental protein 5), a protein that contains two inhibitory domains.
  • Bovine colostrum, serum and spleen trypsin inhibitors.
  • Trypstatin, a rat mast cell inhibitor of trypsin.
  • A number of venom basic protease inhibitors (including dendrotoxins) from snakes.
  • Isoinhibitor K from garden snail.
  • Protease inhibitor from the hemocytes of horseshoe crab.
  • Basic protease inhibitor from red sea turtle.
  • Sea anemone protease inhibitor 5 II.
  • Chymotrypsin inhibitors SCI-I,- II, and -III from silk moth.
  • Trypsin inhibitors A and B from the hemolymph of the tobacco hornworm.
  • Trypsin inhibitor from the hemolymph of the flesh fly [5].
  • Acrosin inhibitor from the male accessory gland of Drosophila.
  • A domain found in one of the alternatively spliced forms of Alzheimer's amyloid β-protein (APP) (also known as protease nexin II) as well as the closely related amyloid-like protein 2 (or APPH).
  • A domain at the C-terminal extremity of the α(3) chain of type VI collagen.
  • A domain at the C-terminal extremity of the α(1) chain of type VII collagen.

We developed a pattern which will only pick up sequences belonging to this family of inhibitors. It spans a region starting after the third cysteine and ending with the fifth one. We also developed a profile that spans the complete domain.

Expert(s) to contact by email:

Ikeo K.

Last update:

April 2006 / Pattern revised.


Technical section

PROSITE methods (with tools and information) covered by this documentation:

BPTI_KUNITZ_2, PS50279; Pancreatic trypsin inhibitor (Kunitz) family profile  (MATRIX)

BPTI_KUNITZ_1, PS00280; Pancreatic trypsin inhibitor (Kunitz) family signature  (PATTERN)


1AuthorsLaskowski M. Jr. Kato I.
TitleProtein inhibitors of proteinases.
SourceAnnu. Rev. Biochem. 49:593-626(1980).
PubMed ID6996568

2TitleSalier J.-P. Inter-alpha-trypsin inhibitor: emergence of a family within the Kunitz-type protease inhibitor superfamily.
SourceTrends Biochem. Sci. 15:435-439(1990).
PubMed ID1703675

3AuthorsIkeo K. Takahashi K. Gojobori T.
TitleEvolutionary origin of a Kunitz-type trypsin inhibitor domain inserted in the amyloid beta precursor protein of Alzheimer's disease.
SourceJ. Mol. Evol. 34:536-543(1992).
PubMed ID1593645

4AuthorsSprecher C.A. Kisiel W. Mathewes S. Foster D.C.
TitleMolecular cloning, expression, and partial characterization of a second human tissue-factor-pathway inhibitor.
SourceProc. Natl. Acad. Sci. U.S.A. 91:3353-3357(1994).
PubMed ID8159751

5AuthorsPapayannopoulos I.A. Biemann K.
TitleAmino acid sequence of a protease inhibitor isolated from Sarcophaga bullata determined by mass spectrometry.
SourceProtein Sci. 1:278-288(1992).
PubMed ID1304909

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