Amino acid sequences of trypsin inhibitors from the melon Cucumis melo.
Two squash family trypsin inhibitors, CMeTI-A and CMeTI-B, were isolated from the melon (Cucumis melo) seeds, by ion exchange chromatography, gel filtration, affinity chromatography, and high-performance liquid chromatography, and their amino acid sequences were determined. All inhibitors contain 29 amino acid residues including 6 half-cystine residues. They differ by twelve amino acid residues. These polypeptides are strong inhibitors of bovine trypsin, with Ki values of 1.6 x 10(-10) M (CMeTI-A) and 4.7 x 10(-10) M (CMeTI-B). The products of CMeTI-A and CMeTI-B cleaved at their reactive sites by tryptic digestion during the purification by trypsin-Sepharose 4B affinity column chromatography are active against trypsin activity, but a molar ratio of inhibitor to trypsin of 2:1 for trypsin-treated CMeTI-B or 1:1 for trypsin-treated CMeTI-A is required.
Institute of Biochemistry, College of Medicine, National Taiwan University, Taipei.
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Lee
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Lin
D000595:Amino Acid Sequence; D000970:Antineoplastic Agents / Q000737:chemistry; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000737:chemistry* / Q000302:isolation & purification; D017386:Sequence Homology, Amino Acid; D014361:Trypsin Inhibitors / Q000737:chemistry* / Q000302:isolation & purification
D000970:Antineoplastic Agents; D010940:Plant Proteins; D014361:Trypsin Inhibitors; C031809:trypsin inhibitor, Cucurbita sp.