[Interaction of phospholipids with 3-oxosteroid-delta 1-dehydrogenase in adsorptional model biomembranes. Interaction of the enzyme from Mycobacterium rubrum with liposomes].
A comparative study of the activity of 3-oxosteroid-delta 1-dehydrogenase from Mycobacterium rubrum 121 in solution and after interaction with liposomes prepared from phospholipids of the same microorganism was carried out. It was demonstrated that at pH 6.6 the enzyme activity in the presence of liposomes is increased. The dependence of this effect on the amount of phospholipids and protein in the system, on the ratio and on the time of their coincubation was established. The activating effect of liposomes is not changed by Mg2+ or EDTA. The crucial role in the enzyme association with the phospholipid matrix belongs to electrostatic bonds which are destroyed upon increase in the ionic strength within the physiological range. The enzyme transition to the free state is accompanied by a fall in the activity. The possible role of these interactions in regulation of enzymatic activity in the cell is discussed.