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Studies on starch breakdown of cereal seeds during anoxic germination

谷物种子缺氧发芽过程中淀粉分解的研究

基本信息

批准号：
07660006
负责人：
YAMAGUCHI Junji
金额：
$ 1.47万
依托单位：
Nagoya University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1995
资助国家：
日本
起止时间：
1995 至 1996
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-07660006/
关键词：
Starch Sugar metabolism Anoxia (germination)alpha-Amylase beta-Amylase Debranching enzyme alpha-Glucosidase Rice

项目摘要

An adequate carbohydrate supply contributes to the survival of seeds under conditions of limited oxygen availability. The amount of soluble, readily fermentable carbohydrates in dry cereal seeds in usually very limited, with starch representing the main storage compound. Starch breakdown during the germination of cereal seeds is the result of the action of hydrolytic enzymes and only through the concerted action of alpha-amylase (EC3.2.1.1), beta-amylase (EC3.2.1.2), debranching enzyme (EC3.2.1.41), and alpha-glucosidase (EC3.2.1.20) can starch be hydrolyzed completely. We present here data concerning the complete set of starch-degrading enzymes in three cereals, rice (Oryza sativa L.), which is tolerant to anaerobiosis, and wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.), which are unable to germinate under anoxia. Among the cereal seeds tested under anoxia, only rice is able to degrade nonboiled, soluble starch, reflecting the ability to degrade the starch granules in vivo. This is explained by the presence of the complete set of enzymes needed to degrade starch completely either as the result of de novo synthesis (alpha-amylase, beta-amylase) or activation of preexisting, inactive form of the enzyme (debranching enzyme, alpha-glucosidase). These enzymes are either absent or inactive in wheat and barley seeds kept under anaerobic conditions.

充足的碳水化合物供应有助于种子在氧气有限的条件下存活。干谷物种子中可溶的、易于发酵的碳水化合物的量通常非常有限，其中淀粉是主要的储存化合物。谷物种子发芽过程中淀粉的分解是水解酶作用的结果，只有通过α-淀粉酶(EC3.2.1.1)、β-淀粉酶(EC3.2.1.2)、脱支酶(EC3.2.1.41)和α-葡萄糖苷酶(EC3.2.1.20)的协同作用，淀粉才能完全水解。我们在此提供了三种谷物中完整的淀粉降解酶的数据，即耐厌氧的水稻 (Oryza sativa L.)，以及在缺氧条件下无法发芽的小麦 (Triticum aestivum L.) 和大麦 (Hordeum vulgare L.)。在缺氧条件下测试的谷物种子中，只有水稻能够降解未煮沸的可溶性淀粉，反映了体内降解淀粉颗粒的能力。这是因为存在完全降解淀粉所需的全套酶，这些酶是从头合成（α-淀粉酶、β-淀粉酶）或预先存在的非活性酶形式（脱支酶、α-葡萄糖苷酶）激活的结果。在厌氧条件下保存的小麦和大麦种子中，这些酶要么不存在，要么没有活性。