TITLE An aspartic type protease degrades trypsin inhibitors, the major root storage proteins of sweet potato (Ipomoea batatas (L.) Lam cv. Tainong 57)
AUTHOR Wen-Chi Hou
Graduate Institute of Pharmacognosy Science, Taipei Medical University, Taipei 110, Taiwan
Dong-Jiann Huang
Institute of Botany, Academia Sinica, Nankang, Taipei 115, Taiwan
Yaw-Huei Lin
Institute of Botany, Academia Sinica, Nankang, Taipei 115, Taiwan
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ABSTRACT Roots of sprouted sweet potato (Ipomoea batatas [L.] Lam) were used as materials to purify proteases which degraded trypsin inhibitors (Tis), the root storage proteins of sweet potato (SP). The commercial pepstatin-agarose (crosslinked, 6%) was chosen as an affinity column for purification. The purified protease has a molecular mass of about 64 kDa on the gelatin-SDS-PAGE gel and was inhibited by pepstatin but not by E-64 on the gelatin-SDS-PAGE gel. Therefore, it might belong to the aspartic type. Using the trypsin inhibitor activity staining method as a criterion for TI degradations, we found that this aspartic type protease could degrade purified Tis in the presence or absence of 5 mM DTT and the hydrolysis was complete in the former condition. The physiological role of aspartic type protease in the degradation of SPTis is discussed.
KEYWORD Aspartic type protease; Degradation; Physiological role; Sweet potato; Trypsin inhibitor;
ARTICLE INFO Botanical Bulletin of Academia Sinica, Volume 43 Number 4 October 2002, page 271-276, 6 pages
PUBLISHER Institute of Plant and Microbial Biology, Academia Sinica, Taipei, Taiwan, Republic of China