Kunitz-type protease inhibitor found in rat mast cells. Purification, properties, and amino acid sequence.
A low molecular weight serine protease inhibitor, named trypstatin, was purified from rat peritoneal mast cells. It is a single polypeptide with 61 amino acid residues and an Mr of 6610. Trypstatin markedly inhibits blood coagulation factor Xa ( Ki = 1.2 x 10(-10) M) and tryptase ( Ki = 3.6 x 10(-10) M) from rat mast cells, which have activities that convert prothrombin to thrombin. It also inhibits porcine pancreatic trypsin ( Ki = 1.4 x 10(-8) M) and chymase ( Ki = 2.4 x 10(-8) M) from rat mast cells, but not papain, alpha-thrombin, or porcine pancreatic elastase. Trypstatin forms a complex in a molar ratio of 1:1 with trypsin and one subunit of tryptase. The complete amino acid sequence of this inhibitor was determined and compared with those of Kunitz-type inhibitors. Trypstatin has a high degree of sequence homology with human and bovine inter-alpha-trypsin inhibitors, A4(751) Alzheimer's disease amyloid protein precursor, and basic pancreatic trypsin inhibitor. However, unlike other known Kunitz-type protease inhibitors, it inhibits factor Xa most strongly.[1]References
- Kunitz-type protease inhibitor found in rat mast cells. Purification, properties, and amino acid sequence. Kido, H., Yokogoshi, Y., Katunuma, N. J. Biol. Chem. (1988) [Pubmed]
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