A Rational Designed PslG With Normal Biofilm Hydrolysis and Enhanced Resistance to Trypsin-Like Protease Digestion

A glycosyl hydrolase produced by Pseudomonas aeruginosa, PslG, has become a promising candidate for biofilm treatment because of its ability to inhibit and disperse biofilms by disrupting exopolysaccharide matrix at nanomolar concentrations. However, as a protein, PslG used for treatment may be degraded by the ubiquitous proteases (of which trypsin-like serine proteases are a major group) secreted by human cells. This would lead to an insufficient effective concentration of PslG. Here, based on the result of liquid chromatography-tandem mass spectrometry (LC-MS/MS) and structural analysis, we generate a PslG mutant (K286A/K433S) with greatly enhanced trypsin resistance. This measure raises IC₅₀ (the concentration of trypsin that can degrade 50% of protein in 30 min at 37°C) from 0.028 mg mL^-1 of the wild-type PslG to 0.283 mg mL^-1 of PslG . In addition, biofilm inhibition assay shows that PslG is much more efficient than wild-type PslG in the presence of trypsin. This indicates that PslG is a better biofilm inhibitor than wild-type PslG in clinical use where trypsin-like proteases widely exist.