A preliminary study of the protease activities in germinating brown rice (Oryza sativa L.) |
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Authors: | Li Cuijuan Cao Xiaohong Gu Zhenxin Wen Huanbin |
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Affiliation: | College of Food Science and Technology, Nanjing Agricultural University, Nanjing, Jiangsu 210095, China. |
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Abstract: | BACKGROUND: Proteases hydrolyse storage proteins to provide precursors for perpetuating species. The aim of this study was to investigate and characterise different proteases in germinating brown rice. RESULTS: The protease activity of brown rice increased sevenfold during 7 days of germination. It was highest on day 6 when determined at pH 3.5. With casein as substrate the proteases showed two catalytic groups: acidic proteases with an optimal pH of 3.5 and alkaline proteases with an optimal pH of 8.0. The acidic protease activity was inhibited by Ba2+ and Pb2+ but stimulated by Zn2+, while the alkaline protease activity was inhibited by Ca2+ and Pb2+ but stimulated by Mg2+ and Zn2+. SDS‐gelatin‐PAGE assay showed two protease activity bands at pH 3.5, while two different bands with higher molecular weights were observed at pH 8.0. Inhibition assay revealed that pepstatin A and E‐64 inhibited 67.63 and 38.26% respectively of the protease activity at pH 3.5, indicating the presence of aspartic and cysteine proteases. Metalloproteases played a major role under alkaline conditions (88.37% inhibition with EDTA). CONCLUSION: Germinated brown rice proteases fall into different classes with different properties. This study is helpful for their further purification. Copyright © 2010 Society of Chemical Industry |
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Keywords: | brown rice germination protease activity bands protease classes |
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