Enzymatic Activity of Cytochrome C-Oxidase Inserted into Magnetoliposomes Differing in Surface Charge Density

The role played by the surface charge density of the phospholipid coat of nanometer-sized Fe₃O₄ colloids (so-called “magnetoliposomes”) in the catalytic activity of beef heart cytochrome c oxidase was investigated. Screening of various binary mixtures of the anionic dimyristoylphosphatidylglycerol and the zwitterionic dimyristoylphosphatidylcholine demonstrated that the highest degree of reactivation was found in the lower negative charge range. Pre-incubation of the charged colloidal biocatalytic particles with cytochrome c induced aggregation and reduced overall enzymatic activity. The results are interpreted in terms of a different affinity of the substrate for the various membrane types and of a reorganisation of the enzyme within the membrane matrices.