Incorporation and activation of a membrane-bound enzyme in bilayers of liposomes

Enzymatic activity and stability ofd-fructose dehydrogenase and sarcosine dehydrogenase immobilizd onto giant vesicles

Stable vesicles with diameters between about 1 and 10 mum were prepared by a particular emulsification technology that involved the use of the surfactants Span 80 and Tween 80 and the phospholipid lecithin (phosphatidylcholine from soybeans). Two membrane enzymes, d-fructose dehydrogenase from Gluconobacter sp. (FDH) and sarcosine dehydrogenase from Pseudomonas putida (SDH), were for the first time immobilized onto the bilayer membranes of these type of vesicles; and the catalytic activity and enzymatic stability were measured and compared with the enzymes in a vesicle-free solution. The enzyme activity as well as stability considerably increased upon immobilization. In particular, immobilized FDH at 25 degrees C was stable for at least 20 days, while the activity of the free enzyme dropped to about 20% of its initial value during the same period of time. In contrast to FDH and SDH, immobilization of sorbitol dehydrogenase from Gluconobacter suboxydans (SODH) was not successful, as no improved activity or stability could be obtained.

Enzyme activity after resealing within ghost erythrocyte cells, and protection by alpha-crystallin against fructose-induced inactivation

The role of alpha-crystallin as a molecular chaperone has been shown in many in vitro studies. In the present paper, we report on the chaperone function of alpha-crystallin within resealed erythrocyte ghosts. Eight enzymes were individually resealed within erythrocyte ghosts and assayed at zero time and at 24 h. The ghost cell suspension was separated into soluble and membrane fractions. Five of the enzymes had significantly greater enzyme activity after 24 h than the control within the soluble fractions. Fructation caused a decrease in enzyme activity (relative to the control). Resealing of alpha-crystallin within the ghost cell alongside the enzymes protected against inactivation by fructose within the soluble fraction.

Interaction of phospholipids with proteins and peptides. New advances III

1. The review deals with the recent achievements in the study of the various interactions of phospholipids with proteins and peptides. 2. The interactions are classified according to the hydrophobic, hydrophilic or mixed character of the interactive forces. 3. The effect of the interaction on the structure and biological activity of the interacting molecules is also discussed.