2001年11月
Roles of the exposed aromatic residues in crystalline chitin hydrolysis by chitinase a from Serratia marcescens 2170
JOURNAL OF BIOLOGICAL CHEMISTRY
- ,
- ,
- ,
- ,
- ,
- 巻
- 276
- 号
- 44
- 開始ページ
- 41343
- 終了ページ
- 41349
- 記述言語
- 英語
- 掲載種別
- 研究論文(学術雑誌)
- DOI
- 10.1074/jbc.M103610200
- 出版者・発行元
- AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
Four exposed aromatic residues, two in the N-terminal domain (Trp-69 and Trp-33) and two in the catalytic domain (Trp-245 and Phe-232) of Serratia marcescens chitinase A, are linearly aligned with the deep catalytic cleft. To investigate the importance of these residues in the binding activity and hydrolyzing activity against insoluble chitin, site-directed mutagenesis to alanine was carried out. The substitution of Trp-69, Trp-33, or Trp-245 significantly reduced the binding activity to both highly crystalline beta -chitin and colloidal chitin. The substitution of Phe-232, which is located closest to the catalytic cleft, did not affect the binding activity. On the other hand, the hydrolyzing activity against beta -chitin microfibrils was significantly reduced by the substitution of any one of the four aromatic residues including Phe-232. None of the mutations reduced the hydrolyzing activity against soluble substrates. These results clearly demonstrate that the four exposed aromatic residues are essential determinants for crystalline chitin hydrolysis. Three of them, two in the N-terminal domain and one in the catalytic domain, play vital roles in the chitin binding. Phe-232 appeared to be important for guiding the chitin chain into the catalytic cleft. Based on these observations, a model for processive hydrolysis of crystalline chitin by chitinase A is proposed.
- リンク情報
- ID情報
-
- DOI : 10.1074/jbc.M103610200
- ISSN : 0021-9258
- Web of Science ID : WOS:000171925600128