Zhang Hua, Shen Wen-Biao, Zhang Wei, Xu Lang-Lai
College of Life Sciences, Nanjing Agricultural University, 210095 Nanjing, P.R. China.
Planta. 2005 Mar;220(5):708-16. doi: 10.1007/s00425-004-1390-7. Epub 2004 Oct 23.
The effects of nitric oxide (NO) and gibberellic acid (GA(3)) on the responses of amylases in wheat (Triticum aestivum L.) seeds (caryopses) were investigated during the first 12 h of germination. GA(3) had no effects on the activities of alpha-amylase (EC 3.2.1.1) or beta-amylase (EC 3.2.1.2), either in intact seeds or embryoless halves within 12 h. In contrast, addition of sodium nitroprusside (SNP), an NO donor, was able to induce a rapid increase in beta-amylase activity without affecting alpha-amylase. Furthermore, the rapid response of beta-amylase to SNP in wheat seeds could be attributed to NO and was approximately dose-dependent. Some other aspects of SNP induction of amylase isozymes were also characterized. Further investigations showed that SNP might play an interesting role in the dissociation of free beta-amylase from small homopolymers or heteropolymers. Furthermore, SNP also directly induced the release of bound beta-amylase from glutenin and its crude enzyme preparation. However, the slight increase in protease also induced by SNP might not be responsible for this action. Interestingly, based on the fact that the rapid response of beta-amylase to NO also existed in seeds of other species, such as barley, soybean, rice and watermelon, it might be a universal event in early seed germination.
在小麦（Triticum aestivum L.）种子（颖果）萌发的最初12小时内，研究了一氧化氮（NO）和赤霉素（GA₃）对淀粉酶反应的影响。在12小时内，GA₃对完整种子或无胚半粒种子中的α-淀粉酶（EC 3.2.1.1）或β-淀粉酶（EC 3.2.1.2）的活性均无影响。相比之下，添加NO供体硝普钠（SNP）能够在不影响α-淀粉酶的情况下迅速提高β-淀粉酶的活性。此外，小麦种子中β-淀粉酶对SNP的快速反应可归因于NO，且大致呈剂量依赖性。还对SNP诱导淀粉酶同工酶的其他一些方面进行了表征。进一步的研究表明，SNP可能在游离β-淀粉酶从小的同聚物或杂聚物的解离中发挥有趣的作用。此外，SNP还直接诱导了谷蛋白及其粗酶制剂中结合的β-淀粉酶的释放。然而，SNP诱导的蛋白酶的轻微增加可能不是此作用的原因。有趣的是，基于其他物种如大麦、大豆、水稻和西瓜的种子中也存在β-淀粉酶对NO的快速反应这一事实，这可能是种子早期萌发中的普遍现象。
