Functional and Structural Effects of Mutagenic Replacement of Asn37 at Subsite F on the Lysozyme-catalyzed Reaction

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To investigate the functional role of subsites E and F in lysozyme catalysis, Asn37 of hen egg-white lysozyme (HEL), which is postulated to participate in sugar residue binding at the right-sided subsite F through hydrogen bonding, was replaced by Ser or Gly by site-directed mutagenesis. The mutations of Asn37 neither significantly affected the binding constant for chitotriose nor the enzymatic activity toward the substrate glycol chitin. However, kinetic analysis with the substrate <I>N</I>-acetylglucosamine pentamer, (GlcNAc)<SUB>5</SUB>, revealed that the conversion of Asn37 to Gly decreased the binding free energies for subsites E and F, while the conversion to Ser increased the substrate affinity at subsite F. It was further found that the rate constant of transglycosylation was reduced by these mutations. These results suggest that Asn37 is involved not only in substrate binding at subsite F but also in transglycosylation activity. No remarkable change in the tertiary structure except the side chain of the 37th residue was detected on X-ray analysis of the mutant proteins, indicating that the alterations in the enzymatic function between the wild type and mutant enzymes depend on limited structural change around the substitution site. It is thus speculated that the slight conformational difference in the side chain of position 37 may affect the substrate and acceptor binding at subsites E and F, leading to lower the efficiency of the transglycosylation activities of the mutant proteins.

収録刊行物

  • Bioscience, biotechnology, and biochemistry

    Bioscience, biotechnology, and biochemistry 68(3), 593-601, 2004-03-23

    Japan Society for Bioscience, Biotechnology, and Agrochemistry

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各種コード

  • NII論文ID(NAID)
    10013142842
  • NII書誌ID(NCID)
    AA10824164
  • 本文言語コード
    ENG
  • 資料種別
    ART
  • ISSN
    09168451
  • NDL 記事登録ID
    6904271
  • NDL 雑誌分類
    ZR7(科学技術--農林水産--農産) // ZR2(科学技術--生物学--生化学) // ZP1(科学技術--化学・化学工業)
  • NDL 請求記号
    Z53-G223
  • データ提供元
    CJP書誌  CJP引用  NDL  J-STAGE 
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