A polysaccharide lyase from Stenotrophomonas maltophilia with a unique, pH-regulated substrate specificity

Area of Science:

• Enzymology
• Microbial Pathogenesis
• Biochemistry

Background:

• Polysaccharide lyases (PLs) are crucial enzymes in microbial pathogenesis, aiding bacterial invasion and biofilm formation.
• Stenotrophomonas maltophilia is a multidrug-resistant bacterium implicated in chronic lung infections, particularly in cystic fibrosis patients.
• Understanding PLs from S. maltophilia is vital for developing new therapeutic strategies against these infections.

Purpose of the Study:

• To characterize a putative alginate lyase (Smlt1473) from Stenotrophomonas maltophilia.
• To investigate the substrate specificity and enzymatic activity of Smlt1473 across various polysaccharides.
• To determine the role of pH in modulating Smlt1473's substrate selectivity.

Main Methods:

• Heterologous expression of Smlt1473 in Escherichia coli.
• One-step purification using affinity chromatography.
• Enzymatic activity and specificity assays using alginate, poly-β-D-glucuronic acid, and hyaluronic acid.
• Analysis of degradation products and determination of pH optima for each substrate.

Main Results:

• Smlt1473 demonstrated broad substrate specificity, degrading alginate, poly-β-D-glucuronic acid, and hyaluronic acid.
• Enzymatic activity was pH-dependent, with optimal degradation occurring at pH 5 (hyaluronic acid), pH 7 (poly-β-D-glucuronic acid), and pH 9 (alginate).
• Degradation products were primarily even-numbered oligomers, indicating endolytic cleavage.

Conclusions:

• Smlt1473 is a multifunctional polysaccharide lyase with broad substrate specificity.
• The enzyme utilizes pH-dependent mechanisms to achieve substrate selectivity.
• This enzyme represents a potential therapeutic target for combating S. maltophilia infections.