Binding of substrate analogs to hen lysozyme in which trp 62 is modified to kynurenine

Keizo Teshima, Seiki Kuramitsu, Kozo Hamaguchi, Fumio Sakiyama, Kensaku Mizuno, Nobuyuki Yamasaki

研究成果: Article

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抜粋

The interactions of β-methyl-GlcNAc, (GlcNAc)2, and (GlcNAc)3 with hen egg-white lysozyme [EC 3.2.1.17] in which Trp 62 is modified to kynurenine (Kyn 62-lysozyme) were studied by measuring the changes in the CD band and fluorescence due to the kynurenine at various pH values. The pH profiles of the binding constants of these saccharides to Kyn 62-lysozyme were very similar to those to intact lysozyme, although the binding constants were lower for the modified lysozyme than for intact lysozyme. The pK values of Asp 52, Glu 35, Asp 48, and Asp 101 in Kyn 62-lysozyme and in its complexes with β-methyl-GlcNAc and with (GlcNAc)2 were in agreement with those of intact lysozyme and its complexes. The pK values of Asp 52 and Glu 35 in the modified lysozyme-(GlcNAc)3 complex were also in agreement with those of the complex with intact lysozyme, but the pK shift of Asp 101 was smaller for Kyn 62-lysozyme than for intact lysozyme. The significance of the decreased binding constants to Kyn 62-lysozyme is discussed.The pH dependence of the CD band due to the kynurenine in Kyn 62-lysozyme was interpreted in terms of the participation of the catalytic groups, Asp 52 (apparent pK 3.5) and Glu 35 (apparent pK 6.0), and the amino group of the kynurenine (apparent pK 0.75). This indicates that the ionization of the catalytic groups affects the state around Trp 62 and supports the previous proposal that there is a relation between the state around Trp 62 and the ionization of Glu 35 (Ikeda, K. & Hamaguchi, K. (1973) J. Biochem. 74, 221-230; (1975) ibid. 77, 1-16; Nakae et al. (1975) J. Biochem. 77, 993-1006). The intrinsic pK value of the amino group of the kynurenine at position 62 shifted from 2.1 to 0.8 on complexing with (GlcNAc)3, indicating interaction between the kynurenine and the sugar residue at subsite B.

元の言語English
ページ(範囲)1015-1027
ページ数13
ジャーナルJournal of biochemistry
87
発行部数4
出版物ステータスPublished - 1980 4 1
外部発表Yes

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology

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  • これを引用

    Teshima, K., Kuramitsu, S., Hamaguchi, K., Sakiyama, F., Mizuno, K., & Yamasaki, N. (1980). Binding of substrate analogs to hen lysozyme in which trp 62 is modified to kynurenine. Journal of biochemistry, 87(4), 1015-1027.