College of Food Science and Technology, Nanjing Agricultural University, Nanjing, Jiangsu 210095, China.
J Sci Food Agric. 2011 Mar 30;91(5):915-20. doi: 10.1002/jsfa.4265.
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.
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 Ba(2+) and Pb(2+) but stimulated by Zn(2+) , while the alkaline protease activity was inhibited by Ca(2+) and Pb(2+) but stimulated by Mg(2+) and Zn(2+) . 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).
Germinated brown rice proteases fall into different classes with different properties. This study is helpful for their further purification.
蛋白酶将储存蛋白水解为维持物种所需的前体。本研究旨在研究和鉴定发芽糙米中的不同蛋白酶。
糙米的蛋白酶活性在发芽的 7 天内增加了 7 倍。在 pH3.5 时，在第 6 天达到最高。以酪蛋白为底物时，蛋白酶显示出两个催化基团：酸性蛋白酶的最适 pH 为 3.5，碱性蛋白酶的最适 pH 为 8.0。酸性蛋白酶活性被 Ba(2+)和 Pb(2+)抑制，但被 Zn(2+)刺激，而碱性蛋白酶活性被 Ca(2+)和 Pb(2+)抑制，但被 Mg(2+)和 Zn(2+)刺激。SDS-凝胶电泳显示 pH3.5 时有两个蛋白酶活性带，而在 pH8.0 时观察到两个分子量更高的不同带。抑制试验表明，胃蛋白酶抑制剂 A 和 E-64 分别抑制 pH3.5 下的蛋白酶活性 67.63%和 38.26%，表明存在天冬氨酸蛋白酶和半胱氨酸蛋白酶。在碱性条件下（EDTA 抑制 88.37%），金属蛋白酶起主要作用。
发芽糙米中的蛋白酶属于不同的类别，具有不同的性质。本研究有助于进一步纯化它们。
