Primary Structure of Dioclea glabra Trypsin Inhibitor, DgTI, a Bowman–Birk Inhibitor

• Published in: Biochemical and biophysical research communications 1999-08, Vol.261 (3), p.838-843
• Main Authors: Bueno, Norlene R, Fritz, Hans, Auerswald, Ennes A, Mentele, Reinhart, Sampaio, Misako, Sampaio, Claudio A.M, Oliva, Maria Luiza V
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; amino acid sequences; Binding Sites; Bowman–Birk inhibitor; Chromatography; Dioclea glabra; Drug Stability; Faboideae; Hydrogen-Ion Concentration; Leguminosae; Molecular Sequence Data; Molecular Weight; Plant Proteins - chemistry; Plant Proteins - isolation & purification; Plant Proteins - metabolism; proteinase inhibitors; seeds; Seeds - chemistry; Sequence Homology; serine proteinase inhibitors; Temperature; Trypsin - metabolism; trypsin inhibitor; Trypsin Inhibitor, Bowman-Birk Soybean - chemistry; Trypsin Inhibitors - chemistry
• ISSN: 0006-291X; 1090-2104
• DOI: 10.1006/bbrc.1999.1099

A novel serine proteinase inhibitor, DgTI, was purified from Dioclea glabra seeds by acetone precipitation, and ion-exchange and reverse phase chromatography. The inhibitor belongs to the Bowman–Birk family, and its primary sequence, determined by Edman degradation and mass spectrometry, of 67 amino acids is: SSGPCCDRCRCTKSEPPQCQCQDVRLNSCHSACEACVCSHSMPGLCSCLDITHFCHEPCKSSGDDED. Although two reactive sites were determined by susceptibility to trypsin (Lys13 and His40), the inhibitory function was assigned only to the first site. The inhibitor forms a 1:1 complex with trypsin, and Ki is 0.5 × 10−9 M. Elastase, chymotrypsin, kallikreins, factor Xa, thrombin, and plasmin were not inhibited. By its properties, DgTI is a Bowman–Birk inhibitor with structural and inhibitory properties between the class of Bowman–Birk type I (with a fully active second reactive site), and Bowman–Birk type II (devoid of second reactive site).