Enzymatic reaction in a vesicular microreactor: peptaibol-facilitated substrate transport.

Catalytic reactions performed with enzymes localized in lipid vesicles or in whole cells represent a new, promising approach in biocatalysis. The delivery of different substrates into these micro- or nano-'reactors' requires a sufficient permeability of lipid membranes. To increase the permeability of lipid bilayers, one may use different membrane-active peptides, including peptaibols. In the present study, the trypsin-catalyzed hydrolysis of N(alpha)-benzoyl-L-arginine-para-nitroanilide (BAPA; 1) was studied in a phospholipid vesicular system made of phosphatidylcholine (POC), in the presence of the peptaibols alamethicin (ALM) or zervamicin IIB (ZER). Two different manners of compartmentalization of substrate and enzyme (enzyme- vs. substrate-containing vesicles) were used. The kinetics parameters of the reaction in homogeneous solution and in the vesicular systems were determined. The rate of the extra- or intravesicular enzymatic reaction was found to be controlled by substrate diffusion through the lipid bilayer. In comparison with untreated vesicular systems, an up to seven-fold increase in reaction rate was observed in the presence of either ALM or ZER.