BILAYER PERMEABILITY-BASED SUBSTRATE SELECTIVITY OF AN ENZYME IN LIPOSOMES

Liposomes were prepared from 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho choline (POPC), which contained the wafer soluble proteinase alpha-chy motrypsin. This liposome entrapped enzyme showed selectivity for exter nally added substrates in that only small substrates (benzoyl-L-Tyr-p- nitroanilide or acetyl-L-Phe-p-nitroanilide)- for which the liposome b ilayer was permeable-were transformed into products. Large substrates (succinyl-L-Ala-L-Ala-L-Pro-L-Phe-p-nitroanilide casein) could not pen etrate from the external aqueous phase into the liposomes, and were no t hydrolyzed. This substrate selectivity is entirely based on the comp artimentation and permeability properties of the liposome microreactor . (C) 1998 John Wiley & Sons, Inc.