The complete amino acid sequence of the Vigna unguiculata (L.) Walp. seed trypsin and chymotrypsin inhibitor

The amino acid sequence of the "double-headed" trypsin and chymotrypsin inhibitor (BTCI), purified from the cowpea Vigna unguiculata (L.) Walp. cv "Seridó" was determined in our laboratory. Tryptic and chymotryptic peptides were sequenced by the Edman-Gray and Edman-Chang N-terminal manual method as well as the carboxypeptidase C-terminal method. The complete amino acid sequence of the BTCI is: Ser-Gly-His-His-Glx-Asx-Ser-Thr-Asx-Glx-Ala-Ser-Glx-Ser-Ser-Lys-Pro-Cys- Cys-Arg- Glx-Cys-Ala-Cys-Thr-Lys-Ser-Ile-Pro-Pro-Glx-Cys-Arg-Cys-Ser-Asx-Val-Arg- Leu-Asn- Ser-Cys-His-Ser-Ala-Cys-Lys-Ser-Cys-Ala-Cys-Thr-Phe-Ser-Ile-Pro-Ala-Glx- Cys-Phe- Cys-Gly-Asx-Ile-Asx-Asx-Phe-Cys-Tyr-Lys-Pro-Cys-Lys-Ser-Ser-His-Ser-Asx- Asx-Asx-Asx-Trp-Asn. BTCI presents a high degree of homology with the Bowman-Birk proteinase inhibitor family.