Journal Article

Characterization of the Reactions of Starch Branching Enzymes from Rice Endosperm

Yasunori Nakamura, Yoshinori Utsumi, Takayuki Sawada, Satomi Aihara, Chikako Utsumi, Mayumi Yoshida and Shinichi Kitamura

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 51, issue 5, pages 776-794
Published in print May 2010 | ISSN: 0032-0781
Published online March 2010 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pcq035
Characterization of the Reactions of Starch Branching Enzymes from Rice Endosperm

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  • Biochemistry
  • Molecular and Cell Biology
  • Plant Sciences and Forestry

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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 ≤40 by attacking not only outer chains but also inner chains of branched glucan while BEIIa or BEIIb could only scarcely or could not attack inner chains, respectively. The comprehensive in vitro studies revealed different enzymatic characteristics of the three BE isozymes and give a new insight into the distinct roles of individual BE isozymes in amylopectin biosynthesis in the endosperm. Based on these results, the functional distinction and interaction of BE isozymes during amylopectin biosynthesis in cereal endosperm is discussed.

Keywords: Amylopectin; Amylose; Rice; Starch biosynthesis; Starch branching enzyme

Journal Article.  10916 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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