Structure and sequence analysis-based engineering of pullulanase from Anoxybacillus sp. LM18-11 for improved...

Area of Science:

• Enzymology
• Protein Engineering
• Biotechnology

Background:

• Pullulanase (EC 3.2.1.41) is a crucial starch-debranching enzyme.
• Improving pullulanase thermostability is essential for its industrial viability.
• The pullulanase from Anoxybacillus sp. LM18-11 was selected for this study.

Purpose of the Study:

• To enhance the thermostability of Anoxybacillus sp. LM18-11 pullulanase.
• To evaluate the effectiveness of combined protein engineering strategies.
• To assess the suitability of engineered pullulanases for industrial applications.

Main Methods:

• Applied a modified amino acid consensus method with residue water-exposed surface analysis.
• Employed deletion of flexible domains, specifically a C-terminal flexible region (D3 mutant).
• Combined these strategies to create multi-mutant enzymes (M17, M18).

Main Results:

• Single mutations and domain deletion (D3) improved thermostability.
• The combined mutant M18 retained 66% activity after 72h at 60°C (wild-type: 35%).
• M18 retained 50.6% activity after 4h at 65°C (wild-type: 16.8%).
• Mutant M17 showed improved catalytic efficiency (Kcat/Km increased by 50%).

Conclusions:

• The engineered pullulanase variants M17 and M18 exhibit significantly enhanced thermostability.
• These mutants demonstrate improved performance under harsh temperature conditions.
• The enhanced properties make M17 and M18 highly promising for industrial enzyme applications.