Báo cáo khoa học: Role of active-site residues of dispersin B, a biofilm-releasing b-hexosaminidase from a periodontal pathogen, in substrate hydrolysis

Role Of Active-Site Residues Of Dispersin B, A Biofilm-Releasing β-Hexosaminidase From A Periodontal Pathogen, In Substrate Hydrolysis

Authors: Suba G. A. Manuel, Chandran Ragunath, Hameetha B. R. Sait, Era A. Izano, Jeffrey B. Kaplan and Narayanan Ramasubbu

Field: Molecular Biology / Biochemistry

Document Summary: This study investigates the role of active-site residues in dispersin B (DspB), a β-hexosaminidase from the oral pathogen *Aggregatibacter actinomycetemcomitans*, which cleaves β(1,6)-linked N-acetylglucosamine polymers and is involved in biofilm detachment. Through site-directed mutagenesis, researchers identified key residues, including acidic pairs (D183, E184) and E332, that are critical for substrate hydrolysis. The study also highlights the importance of aromatic residues (Y187, Y278, W237, W330) and arginine (R27) in substrate binding, specificity, and transition state stabilization. The findings suggest that DspB employs a substrate-assisted mechanism for hydrolysis, with specific residues orienting the N-acetyl group and stabilizing the transition state. This research contributes to understanding the enzymatic mechanism of β-hexosaminidases and their role in bacterial pathogenesis.

Detailed Table of Contents:

• Introduction to Dispersin B and its role
• Keywords
• Correspondence
• Role of active-site residues (Acidic and Aromatic)
• Results of Mutational Analysis
• pH Activity Profiles
• Biofilm Detachment and Hydrolytic Activities
• Discussion of findings
• Experimental Procedures (Expression, Purification, Enzyme Assays, pH Optima, Bacterial Strains, Biofilm Assays)
• Acknowledgements
• References