Alpha 2-antiplasmin's carboxy-terminal lysine residue is a major site of interaction with plasmin |
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Authors: | G L Hortin B L Gibson K F Fok |
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Institution: | Department of Pediatrics, Washington University, St. Louis, MO 63110. |
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Abstract: | alpha 2-Antiplasmin (AP) inhibits plasmin in a two-step reaction in which AP reversibly binds to lysine-binding sites of plasmin and, then, more slowly complexes covalently with the enzyme's active site. Here, we show that the C-terminal lysine residue of AP has a key role in binding of the inhibitor to plasmin. A synthetic peptide corresponding to the C-terminal 26 amino acid residues of AP blocked association of AP with plasmin, but this activity of the peptide was lost when its C-terminal lysine residue was removed with carboxypeptidase B. The essential role of this lysine residue was shown more directly by treating AP with carboxypeptidase B and observing that AP lost its ability to inhibit plasmin rapidly. |
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