THE NATURE OF PHOSPHOLIPASE C FROM ACINETOBACTER CALCOACETICUS: EFFECTS ON WHOLE RED CELLS AND RED CELL MEMBRANES

Publisher Website
Google Scholar
Abstract
The effect of chelating agents and divalent metal ions on the enzymatic reaction of phospholipase C (haemolysin) of Acinetobacter calcoaceticus has been examined. Various phospholipids have been tested for their interference with phospholipase C‐induced haemolysis. The effects of the enzyme on red cell membrane phospholipids and red cell membrane adenosine triphosphatase (ATP‐ase) activities have been examined. In accordance with previous investigations, the total enzymatic activity (TA) was found to consist of a basal activity (BA) in the absence of Mg2+, plus an increase in activity induced by the addition of Mg2+ (MgA). Treatment of phospholipase C with 5 mM ethylendiaminetetraacetate (EDTA) prior to incubation with substrate, completely inactivated the enzyme. Addition of 5 mM Mg2+ restored 27 per cent of TA, while 0.1 mM Zn2+ did not reactivate the enzyme. The inhibitory effect of EDTA in the incubation mixture was overcome by Mg2+. In the haemolytic reaction, Zn2+ inhibited MgA in concentrations that had no detectable effect on BA. Micellar phospholipids were shown to have an inhibitory effect on haemolytic activity. The enzyme attacked lecithin, phosphatidylethanolamine and sphingomyelin of the red cell membrane, liberating 69 per cent of the membrane‐bound acid soluble phosphorus. Both ouabain‐sensitive and ‐insensitive ATP‐ase activities were partly inactivated.

This publication has 21 references indexed in Scilit: