| Research Abstract |
First, interaction of calpains with kininogens were studied. It was found that calcium ion was required for the binding and that the inhibition of calpains by kininogens was accompanied by a simultaneous fragmentation of kininogen and the autodigestion of calpain itself. It was also revealed that when high molecular weight kininogen was digested by plasmin, ALPHA_1-thiol proteinase inhibitor was generated, releasing kinin and fragment 1・2.
Second, we found that chemotactic activity for polymorphonuclear leucocytes (PMN) was produced in the autodigest of calpain 1 purified from human erythrocytes. An active peptide was isolated from the autodigest and its chemical structure was determined. It was an acetylated nonapeptide with a sequence of acetyl Ser-Glu-Glu-Ile-Ile-Thr-Pro-Val-Tyr. In comparison with the entire sequence of human calpain I, this peptide was compatible with the N-terminal amino acid sequence of the large subunit of calpain I, whose primary structure was deduced from cDNA sequence, except that the peptide was demetionyl and acetylated at the N-terminus. The peptide was chemically synthesized and the chemotactic activity was reconfirmed by both in vitro experiment: assay in chemotactic microchembers and in vivo experiment: histological abservations after subcutaneous injection of the peptide. Several other peptides with amino acid sequences in n-termini of large and small subunits of calpains I and II were also synthesized and the chemotactic activity was examined. In addition to the above peptide, acetylated tri-, tetra-, and nona-peptides with the amino acid sequence in n-terminus of small subunit were shown to have the chemotactic activity.
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