Biochemical characterisation of a glycogen branching enzyme from Streptococcus mutans: Enzymatic modification of starch

Eun Joo Kim, Soo In Ryu, Hyun Ah Bae, Nguyen Thi Huong, Soo Bok Lee

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Abstract

A gene encoding a putative glycogen branching enzyme (SmGBE) in Streptococcus mutans was expressed in Escherichia coli and purified. The biochemical properties of the purified enzyme were examined relative to its branching specificity for amylose and starch. The activity of the approximately 75 kDa enzyme was optimal at pH 5.0, and stable up to 40 °C. The enzyme predominantly transferred short maltooligosyl chains with a degree of polymerization (dp) of 6 and 7 throughout the branching process for amylose. When incubated with rice starch, the enzyme modified its optimal branch chain-length from dp 12 to 6 with large reductions in the longer chains, and simultaneously increased its branching points. The results indicate that SmGBE can make a modified starch with much shorter branches and a more branched structure than to native starch. In addition, starch retrogradation due to low temperature storage was significantly retarded along with the enzyme reaction.

Original languageEnglish
Pages (from-to)979-984
Number of pages6
JournalFood Chemistry
Volume110
Issue number4
DOIs
Publication statusPublished - 2008 Oct 15

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All Science Journal Classification (ASJC) codes

  • Analytical Chemistry
  • Food Science

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