Biochemical characterization of 4-α-glucanotransferase from Saccharophagus degradans 2-40 and its potential role in glycogen degradation

Authors

  • Sungmin Hwang,

    1. The Microbiological Resource Research Institute, Pusan National University, Busan, Korea
    2. Department of Microbiology, College of Natural Sciences, Pusan National University, Busan, Korea
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  • Kyoung-Hwa Choi,

    1. Department of Microbiology, College of Natural Sciences, Pusan National University, Busan, Korea
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  • Jieun Kim,

    1. School of Biological Sciences and Institute of Microbiology, Seoul National University, Seoul, Korea
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  • Jaeho Cha

    Corresponding author
    1. Department of Microbiology, College of Natural Sciences, Pusan National University, Busan, Korea
    • The Microbiological Resource Research Institute, Pusan National University, Busan, Korea
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Correspondence: Jaeho Cha, Department of Microbiology, Pusan National University, Busandaehak-ro 63beon-gil 2, Geumjeong-gu, Busan 609-735, Korea. Tel.: +82 51 510 2196; fax: +82 51 514 1778; e-mail: jhcha@pusan.ac.kr

Abstract

4-α-Glucanotransferase, an enzyme encoded by malQ, transfers 1,4-α-glucan to an acceptor carbohydrate to produce long linear maltodextrins of varying lengths. To investigate the biochemical characteristics of the malQ gene (Sde0986) from Saccharophagus degradans 2-40 and to understand its physiological role in vivo, the malQ gene was cloned and expressed in Escherichia coli. The amino acid sequence of MalQ was found to be 36–47% identical to that of amylomaltases from gammaproteobacteria. MalQ is a monomeric enzyme that belongs to a family of 77 glycoside hydrolases, with a molecular mass of 104 kDa. The optimal pH and temperature for MalQ toward maltotriose were determined to be 8.5 and 35 °C, respectively. Furthermore, the enzyme displayed glycosyl transfer activity on maltodextrins of various sizes to yield glucose and long linear maltodextrins. MalQ, however, could be distinguished from other bacterial and archaeal amylomaltases in that it did not produce maltose and cyclic glucan. Reverse transcription PCR results showed that malQ was not induced by maltose and was highly expressed in the stationary phase. These data suggest that the main physiological role of malQ in S. degradans is in the degradation of glycogen, although the gene is commonly known to be involved in maltose metabolism in E. coli.

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