Characterization of the reactions of starch branching enzymes from rice [Oryza sativa] endosperm

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...

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Bibliographic Details
Published in:Plant and cell physiology 2010-05, Vol.51 (5), p.776-794
Main Authors: Nakamura, Y., Akita Prefectural Univ. (Japan). Faculty of Bioresource Sciences, Utsumi, Y, Sawada, T, Aihara, S, Utsumi, C, Yoshida, M, Kitamura, S
Format: Article
Language:English
Subjects:
1,4-alpha-Glucan Branching Enzyme - metabolism
ALMIDON
AMIDON
AMILOPECTINA
AMILOSA
AMYLOPECTIN
Amylopectin - metabolism
AMYLOPECTINE
AMYLOSE
Amylose - metabolism
BIOSINTESIS
BIOSYNTHESE
BIOSYNTHESIS
ENDOSPERM
Endosperm - enzymology
ENDOSPERMA
ENDOSPERME
enzyme activity
enzymes
Freshwater
http://www.fao.org/aos/agrovoc#c_15987
http://www.fao.org/aos/agrovoc#c_2561
http://www.fao.org/aos/agrovoc#c_371
http://www.fao.org/aos/agrovoc#c_372
http://www.fao.org/aos/agrovoc#c_5438
http://www.fao.org/aos/agrovoc#c_7369
http://www.fao.org/aos/agrovoc#c_928
in vitro studies
ISOENZIMAS
ISOENZYME
ISOENZYMES
Isoenzymes - metabolism
isozymes
Oryza - enzymology
ORYZA SATIVA
Plant Proteins - metabolism
polymerization
Rice
STARCH
Starch biosynthesis
Starch branching enzyme
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Summary: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.
ISSN:0032-0781
1471-9053
DOI:10.1093/pcp/pcq035