Purification and structural stability of a trypsin inhibitor from Amazon Inga cylindrica [Vell.] Mart. seeds

Inga cylindrica Trypsin Inhibitor (ICTI) was purified as a single polypeptide chain by one step anion-exchange chromatography from a crude extract of Inga cylindrica (Vell.) Mart. seeds. ICTI is a 19.5 kDa protein presenting a remarkable inhibitory activity against bovine trypsin (EC 3.4.21.4) (Ki = 4.3 nM). Circular dichroism analysis revealed that this inhibitor is a β type protein (40.4% of β-strand; 24.6% of β-turn and 6.7% of α-helix) in accordance with properties displayed in Kunitz type inhibitors. ICTI is a thermal stable protein within a wide range of pH (1.6 to 10.0) exhibiting h...

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