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The characterization of modified starch branching enzymes: toward the control of starch chain-length distributions.


ABSTRACT: Starch is a complex branched glucose polymer whose branch molecular weight distribution (the chain-length distribution, CLD) influences nutritionally important properties such as digestion rate. Chain-stopping in starch biosynthesis is by starch branching enzyme (SBE). Site-directed mutagenesis was used to modify SBEIIa from Zea mays (mSBEIIa) to produce mutants, each differing in a single conserved amino-acid residue. Products at different times from in vitro branching were debranched and the time evolution of the CLD measured by size-exclusion chromatography. The results confirm that Tyr352, Glu513, and Ser349 are important for mSBEIIa activity while Arg456 is important for determining the position at which the linear glucan is cut. The mutant mSBEIIa enzymes have different activities and suggest the length of the transferred chain can be varied by mutation. The work shows analysis of the molecular weight distribution can yield information regarding the enzyme branching sites useful for development of plants yielding starch with improved functionality.

SUBMITTER: Li C 

PROVIDER: S-EPMC4395411 | biostudies-literature | 2015

REPOSITORIES: biostudies-literature

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The characterization of modified starch branching enzymes: toward the control of starch chain-length distributions.

Li Cheng C   Wu Alex Chi AC   Go Rob Marc RM   Malouf Jacob J   Turner Mark S MS   Malde Alpeshkumar K AK   Mark Alan E AE   Gilbert Robert G RG  

PloS one 20150413 4


Starch is a complex branched glucose polymer whose branch molecular weight distribution (the chain-length distribution, CLD) influences nutritionally important properties such as digestion rate. Chain-stopping in starch biosynthesis is by starch branching enzyme (SBE). Site-directed mutagenesis was used to modify SBEIIa from Zea mays (mSBEIIa) to produce mutants, each differing in a single conserved amino-acid residue. Products at different times from in vitro branching were debranched and the t  ...[more]

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