1. Effects of dockerin domains on Neocallimastix frontalis xylanases.
- Author
-
Huang YH, Huang CT, and Hseu RS
- Subjects
- Amino Acid Sequence, Circular Dichroism, Endo-1,4-beta Xylanases genetics, Endo-1,4-beta Xylanases metabolism, Hydrogen-Ion Concentration, Molecular Sequence Data, Recombinant Proteins genetics, Recombinant Proteins metabolism, Sequence Deletion, Substrate Specificity, Temperature, Xylosidases genetics, Xylosidases metabolism, beta-Glucosidase genetics, beta-Glucosidase metabolism, Endo-1,4-beta Xylanases chemistry, Gene Expression Regulation, Fungal, Neocallimastix enzymology, Xylans metabolism, Xylosidases chemistry, beta-Glucosidase chemistry
- Abstract
Two xylanase genes were cloned from the anaerobic fungus Neocallimastix frontalis. Xyn11A had a modular structure of two catalytic domains and two dockerin domains, while Xyn11B had one catalytic domain and two dockerin domains. The characteristics of the xylanases with and without dockerin domains were investigated. The deletion of dockerin domains had little influence on the optimal pH of xylanases, while it significantly affected the optimal temperatures. The optimal temperatures increased from 55 to 60 degrees C for Xyn11A and 60 to 65 degrees C for Xyn11B after the deletion of dockerin domains. The increase of optimal temperatures was attributed to the lower stability of the second structure in full length xylanase than that in the truncated one as evidenced by the circular dichroism spectroscopy. The specific activity of Xyn11A and Xyn11B increased about 64% and 330%, respectively, after the deletion of the dockerin domains. The removal of dockerin domains appeared to increase the overall efficiency of Xyn11A' (1.2-) and Xyn11B' (2.9-) fold with oat spelts xylan as reflected by the values of k(cat)/K(m). The results suggest that the dockerin domain might play an important role in the characteristics of xylanases from anaerobic fungi.
- Published
- 2005
- Full Text
- View/download PDF