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BioMed Research International
Volume 2014 (2014), Article ID 379234, 9 pages
Research Article

Angiotensin I-Converting Enzyme Inhibitor Derived from Cross-Linked Oyster Protein

1Department of Seafood Science and Technology/Institute of Marine Industry, Gyeongsang National University, Gyeongnam-do 650-160, Republic of Korea
2Department of Pharmaceutical Engineering, College of Medical and Life Science, Silla University, Busan 617-736, Republic of Korea
3Department of Hygienic Chemistry, College of Pharmacy, Kyung Hee University, Seoul 130-701, Republic of Korea

Received 11 April 2014; Revised 7 June 2014; Accepted 24 June 2014; Published 23 July 2014

Academic Editor: Stelvio M. Bandiera

Copyright © 2014 Cheng-Liang Xie et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Following cross-linking by microbial transglutaminase, modified oyster proteins were hydrolyzed to improve inhibitory activity against angiotensin-converting enzyme (ACE) inhibitory activity with the use of a single protease, or a combination of six proteases. The oyster hydrolysate with the lowest 50% ACE inhibitory concentration (IC50) of 0.40 mg/mL was obtained by two-step hydrolysis of the cross-linked oyster protein using Protamex and Neutrase. Five ACE inhibitory peptides were purified from the oyster hydrolysate using a multistep chromatographic procedure comprised of ion-exchange, size exclusion, and reversed-phase liquid chromatography. Their sequences were identified as TAY, VK, KY, FYN, and YA, using automated Edman degradation and mass spectrometry. These peptides were synthesized, and their IC50 values were measured to be 16.7, 29.0, 51.5, 68.2, and 93.9 μM, respectively. Toxicity of the peptides on the HepG2 cell line was not detected. The oyster hydrolysate also significantly decreased the systolic blood pressure of spontaneously hypertensive rats (SHR). The antihypertensive effect of the oyster hydrolysate on SHR was rapid and long-lasting, compared to commercially obtained sardine hydrolysate. These results suggest that the oyster hydrolysate could be a source of effective nutraceuticals against hypertension.