By the use of strains that differ in their ability of producing LipA indicated that the major activity of extracellular lipase is due to the presence of lipase LipA. Binding of lipase

LipA to alginate Previous in vitro studies have demonstrated the stimulation of lipase release from non-mucoid wild-type P. aeruginosa by the addition of purified algal and bacterial alginate to cell suspensions. Moreover, the interaction of lipases and algal alginate with a concomitant stabilization of the enzyme against ethanol-induced denaturation was shown in vitro. On the basis of these observations we hypothesized that extracellular lipase in mucoid P. aeruginosa biofilms might be bound to the alginate in the EPS matrix. Therefore, in vitro binding studies in a microtiter plate assay were conducted using purified LipA from P. aeruginosa and bacterial alginate A1331852 isolated from mucoid P. aeruginosa SG81 biofilms. For comparison, different neutral (dextran, levan) and negatively charged polysaccharides (algal alginate, xanthan) were tested. The immobilization of the polysaccharides on the Lorlatinib molecular weight polystyrene of the microtiter plate was verified by carbohydrate quantification. Binding of polysaccharides to wells of polystyrene Vismodegib purchase microtiter

plates in a concentration of 0.01 – 1.0 mg/ml was also shown before [48]. After two washing steps with 200 μl water each, a significantly increased lipase activity was Oxymatrine detected in the wells of the microtiter plate with increasing amounts of bacterial alginate

used for coating of the wells (Figure 2). This observation indicated that LipA bound to the immobilized bacterial alginate in a concentration-dependent manner. In the absence of polysaccharides no lipase activity was detected within the microtiter plate after the performed washing steps (∆A405 ≤ 0.07) indicating that LipA did not bind to the polystyrene surface (Figure 2). Without washing the lipase activity was ∆A405 = 0.8 +/− 0.1 independent of the presence or absence of polysaccharides. This result indicated that no interfacial activation of the lipase occurs by the presence of polysaccharides. It was reported that the enzyme exhibits a permanent open conformation [13]. Interestingly, no binding of LipA to the neutral polysaccharide dextran (poly-α-D-glucose) and only minor binding of LipA to levan (poly-β-D-fructose) was detected. These results suggested an influence of negative charges of the polysaccharides on the binding of lipase. A binding of LipA to xanthan was observed only at high concentrations of the polysaccharide. Xanthan is a heteropolymer of glucose, mannose and glucuronic acid, which is substituted with acetate and pyruvate residues. Therefore, this polysaccharide displays neutral as well as anionic properties and thus the charge density of xanthan was reduced in relation to alginate.