Improving the catalytic performance of xylanase from Bacillus circulans through structure-based rational design

Area of Science:

• Enzymology
• Biotechnology
• Protein Engineering

Background:

• Endo-1,4-β-xylanase is crucial for converting hemicellulose into fermentable sugars in biorefineries.
• Bacillus circulans xylanase (Bcx) is a key enzyme in this process, but its catalytic performance can be enhanced.
• Understanding enzyme flexibility is vital for optimizing catalytic activity.

Purpose of the Study:

• To improve the catalytic performance of Bacillus circulans xylanase (Bcx) through structure-guided rational design.
• To investigate the role of the R49 residue in Bcx's conformational flexibility and substrate binding.
• To engineer novel Bcx variants with enhanced enzymatic properties.

Main Methods:

• Systematic analysis of flexible motions in Bcx to identify key regulatory components.
• Site-saturated mutagenesis targeting the R49 residue.
• Characterization of mutant enzymes for catalytic efficiency, conformational stability, and product profiles.

Main Results:

• The R49 residue was identified as a constraint on global conformational changes and a modulator of flexible motion.
• Mutagenesis at R49 yielded active variants, balancing enzyme flexibility and rigidity.
• The R49N mutant demonstrated a 7.51-fold increase in catalytic efficiency and improved production of xylobiose and xylotriose.

Conclusions:

• Rational design targeting enzyme flexibility can significantly enhance catalytic performance.
• The R49N mutant of Bcx represents a promising enzyme for industrial applications in biorefining.
• Controlling enzyme flexibility is a viable strategy for improving industrially relevant enzymes.