Starch-biosynthesis enzymes producing the less stickiness of boiled rice of indica variety

淀粉生物合成酶降低籼米的粘性

• 批准号: 07660171
• 负责人: TAKEDA Yasuhito
• 金额: $ 1.47万
• 依托单位: Kagoshima 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-07660171/
• 关键词: branching enzyme; structure of amylopectin; starch biosynthesis; boiled rice; indica rice; japonica rice; ジャポニカ; アミロペクチンの構造

Boiled rice of indica variety is less sticky compared with that of japonica variety, being suggested to be due to a higher amount of very long chains of indica amylopectin. Therefore, we examined branching enzyme from rice endosperm of indica and japonica varieties because the enzyme, out of enzymes involving starch biosynthesis, may have an important role to produce short and very long chains of amylopectin. Among six varieties examined here of indica and japonica rices, Saikai 184 variety had a typical type of indica amylopectin and Saikai 194 had that of japonica amylopectin having a small amount of very long chains. Immature endosperms (about 20 days after pollination) of Saikai 184 and Saikai 194 had at least two isoforms of branching enzyme with a various amount when examined by activity staining after gel electrophoresis. A major isoform was purified to be essentially free of amylase by chromatography on butyl-Toyopearl 650S,DEAE-Sepharose FF,Mono Q,Superose 12 and amylose-Sepharose 6B.Both preparations showed a similar ratio of the activities determined by the phosporylase stimulation assay and the branch linkage assay, and were found to transfer preferentially long chains when they were incubated with reduced amylose as a substrate. This type of chain transfer resembled that for maize BE-I isoform, but differed from that for maize BE-II isoform and for kidney bean enzyme which preferentially transferred short chains. However, the rice isoform and maize BE-I differed in producing a relatively high amount of chains with d. p. 10-12 and of a chain with d. p. 6, respectively. This result might imply that such an intrinsic chain transfer action determines chain-length distribution of amylopection in plant origin. The less stickiness of indica boiled rice might be clarified by further experiments on catalytic functions of starch synthase and /or minor isoform of branching enzyme.

与粳稻品种相比，籼稻品种的米饭粘度较低，这可能是由于糯米中含有较多的超长支链淀粉所致。因此，我们研究了水稻品种水稻胚乳中的分支酶，因为在参与淀粉生物合成的酶中，这种酶可能对产生支链淀粉的短链和超长链起重要作用。在所研究的6个水稻品种中，塞开184的支链淀粉具有典型的类型，而塞开194的支链支链有少量的极长链。塞开184和塞开194的未成熟胚乳(授粉后20d左右)至少有两种不同程度的分支酶。经丁基-TOYOPEL 650S、DEAE-SepharoseFF、Mono Q、Superose 12和直链淀粉-Sepharose6B柱层析，得到一个基本不含淀粉酶的主要异构体。两种制剂的活性比率与磷孢素酶刺激试验和支链分析结果相似，并且当它们与还原的直链淀粉孵育时，它们优先转移长链。这种类型的链转移与玉米BE-I亚型相似，但不同于玉米BE-II亚型和优先转移短链的菜豆酶。然而，水稻异构体和玉米BE-I的不同之处在于分别产生了相对较高数量的具有d.p.10-12的链和具有d.p.6的链。这一结果可能暗示，这种内在的链转移作用决定了植物起源的支链淀粉的链长分布。进一步对淀粉合成酶和/或分支酶的次要异构体的催化作用进行实验，可以阐明糯米粘性较差的原因。

项目成果

水上浩之、竹田靖史、檜作進: "新形質米の澱粉の構造と性質" 応用糖質科学. 43. 15-23 (1996)

Hiroyuki Mizukami、Yasushi Takeda、Susumu Hisaku：“新稻米品种中淀粉的结构和特性”Applied Glycoscience 43. 15-23 (1996)。

H.MIZUKAMI,Y.TAKEDA and S.HIZUKURI: "Structures and pasting properties of starches from new characteristic rice cultivars (in Japanese)" Oyo Toshitu Kagau. 43. 15-23 (1996)

H.MIZUKAMI、Y.TAKEDA 和 S.HIZUKURI：“新特色水稻品种淀粉的结构和糊化特性（日语）”Oyo Toshitu Kagau。

水上浩之、檜作進、竹田靖史: "新形質米の澱粉の構造と性質" 応用糖質科学. 43. 15-23 (1996)

Hiroyuki Mizukami、Susumu Hizusaku、Yasushi Takeda：“新开发的大米中淀粉的结构和特性”Applied Glycoscience 43. 15-23 (1996)。

水上浩之,竹田靖史,檜作進: "新形質米の澱粉の構造と性質" 応用糖質科学. (印刷中).

Hiroyuki Mizukami、Yasushi Takeda、Susumu Hizaku：“新水稻品种中淀粉的结构和特性”应用糖科学（正在出版）。