Characterization of the Reactions of Starch Branching Enzymes from Rice Endosperm
Characterization of the Reactions of Starch Branching Enzymes from Rice Endosperm
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DOI：
10.1093/pcp/pcq035
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发表时间：
2010-05-01
影响因子：
4.9
通讯作者：
Kitamura, Shinichi
中科院分区：
文献类型：
--
作者：
Nakamura, Yasunori;Utsumi, Yoshinori;Kitamura, Shinichi
据我们所知，本文首次从支链淀粉和合成直链淀粉作为葡聚糖底物的水稻中得到了三种淀粉分支酶（BE）同工酶BEI、BEIIa和BEIIb的动力学参数。BE同工酶对直链葡聚糖直链淀粉的活性随着直链淀粉摩尔大小的减小而降低，当直链淀粉的聚合度（DP）低于80时，BEIIa和BEIIb不存在活性，而BEI对直链淀粉的聚合度（DP）高于50左右时，BEI具有活性。对BE反应脱支产物的详细分析揭示了个体BE同工酶的不同链长偏好。BEIIb几乎完全转移了DP7和DP6的链，而BEIIa从支链淀粉和直链淀粉的外链形成了DP6到DP15周围的广泛短链。另一方面，BEI形成了DP的多种短链和中间链
To our knowledge the present paper shows for the first time the kinetic parameters of all the three starch branching enzyme (BE) isozymes, BEI, BEIIa and BEIIb, from rice with both amylopectin and synthetic amylose as glucan substrate. The activities of these BE isozymes with a linear glucan amylose decreased with a decrease in the molar size of amylose, and no activities of BEIIa and BEIIb were found when the degree of polymerization (DP) of amylose was lower than at least 80, whereas BEI had an activity with amylose of a DP higher than approximately 50. Detailed analyses of debranched products from BE reactions revealed the distinct chain length preferences of the individual BE isozymes. BEIIb almost exclusively transferred chains of DP7 and DP6 while BEIIa formed a wide range of short chains of DP6 to around DP15 from outer chains of amylopectin and amylose. On the other hand, BEI formed a variety of short chains and intermediate chains of a DP