Enzymatic reactions in liposomes using the detergent-induced liposome loading method

Microcompartmentalization is a crucial step in the origin of life. More tha n 30 years ago, Oparin et al. proposed models based on biochemical reaction s taking place in so-called coacervates. Their intention was to develop sys tems with which semipermeable microcompartments could be established. In th e present work we follow their intuition, but we use well-characterized bil ayer structures instead of the: poorly characterized coacervates. Liposomes from phospholipids can be used as microreactors but they exhibit only a mo dest permeability and, therefore, chemical reactions occurring inside these structures are depleted after a relatively short period. Here it is shown that even highly stable liposomes from 1-palmitoyl-2-oleoyl-sn-glycero-3-ph osphocholine (POPC) can be used as semipermeable microreactors when treated with sodium cholate. Using this kind of mixed liposomes, we describe a bio chemical reaction occurring inside the liposomes while the same reaction is prevented in the external medium. In addition, we show that this cholate-i nduced permeability of POPC bilayers can even be used to load macromolecule s such as enzymes from the outside. (C) 1999 Elsevier Science B.V. All righ ts reserved.