KMID : 0545120210310010043
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Journal of Microbiology and Biotechnology 2021 Volume.31 No. 1 p.43 ~ p.50
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Comparison of Catalyzing Properties of Bacterial 4-¥á-Glucanotransferases Focusing on Their Cyclizing Activity
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Kim Jung-Eun
Tran Phuong Lan Ko Jae-Min Kim Sa-Rang Kim Jae-Han Park Jong-Tae
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Abstract
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A newly cloned 4-¥á-glucanotransferase (¥áGT) from Deinococcus geothermalis and two typical bacterial ¥áGTs from Thermus scotoductus and Escherichia coli (MalQ) were investigated. Among 4 types of catalysis, the cyclization activity of ¥áGTs that produces cycloamylose (CA), a valuable carbohydrate making inclusion complexes, was intensively studied. The new ¥áGT, Dg¥áGT, showed close protein sequence to the ¥áGT from T. scotoductus (Ts¥áGT). MalQ was clearly separated from the other two ¥áGTs in the phylogenetic and the conserved regions analyses. The reaction velocities of disproportionation, cyclization, coupling, and hydrolysis of three ¥áGTs were determined. Intriguingly, MalQ exhibited more than 100-fold lower cyclization activity than the others. To lesser extent, the disproportionation activity of MalQ was relatively low. Dg¥áGT and Ts¥áGT showed similar kinetics results, but Ts¥áGT had nearly 10-fold lower hydrolysis activity than Dg¥áGT. Due to the very low cyclizing activity of MalQ, Dg¥áGT and Ts¥áGT were selected for further analyses. When amylose was treated with Dg¥áGT or Ts¥áGT, CA with a broad DP range was generated immediately. The DP distribution of CA had a bimodal shape (DP 7 and 27 as peaks) for the both enzymes, but larger DPs of CA quickly decreased in the Dg¥áGT. Cyclomaltopentaose, a rare cyclic sugar, was produced at early reaction stage and accumulated as the reactions went on in the both enzymes, but the increase was more profound in the Ts¥áGT. Taken together, we clearly demonstrated the catalytic differences between ¥áGT groups from thermophilic and pathogenic bacteria that and showed that ¥áGTs play different roles depending on their lifestyle.
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KEYWORD
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4-¥á-Glucanotransferase, cycloamylose, cyclization, disproportionation, cyclic maltopentaose
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