title: Effect of Co2+-substitution on the substrate specificity of phospholipase C from Bacillus cereus during attack on two membrane systems.
abstract: Phospholipid degradation by native phospholipase C from Bacillus cereus and enzyme forms where one or both of the Zn2+ prosthetic groups had been replaced with Co2+ was studied in human erythrocyte membranes (ghosts) and resuspended freeze-dried bovine brain myelin. The rate of total phospholipid degradation was 2-9-fold more rapid with erythrocytes than with myelin. With both membrane systems the activity decreased in the order ZnZn-enzyme greater than ZnCo-enzyme greater than CoCo-enzyme. For all three enzyme forms with either membrane system, phosphatidylethanolamine (or the ethanolamine-containing phosphoglycerides) and phosphatidylcholine were hydrolysed most rapidly and sphingomyelin least. The relative rate of sphingomyelin degradation was highest with the ZnCo-enzyme. In myelin at low ionic strength there seemed to be a core of phospholipid that was very resistant to degradation by native phospholipase C but which was much more accessible to the Co2+-substituted forms. It is suggested that ZnCo-phospholipase C has potential applications in membrane studies.
mesh_terms: D000818:Animals; D001409:Bacillus cereus / Q000201:enzymology*; D002417:Cattle; D002462:Cell Membrane / Q000378:metabolism; D003035:Cobalt / Q000494:pharmacology*; D004910:Erythrocyte Membrane / Q000378:metabolism; D006801:Humans; D006868:Hydrolysis; D066298:In Vitro Techniques; D009186:Myelin Sheath / Q000378:metabolism; D010740:Phospholipases / Q000378:metabolism*; D010743:Phospholipids / Q000097:blood / Q000378:metabolism; D013379:Substrate Specificity; D010738:Type C Phospholipases / Q000378:metabolism*; D015032:Zinc / Q000494:pharmacology
chemical_list: D010743:Phospholipids; D003035:Cobalt; D010740:Phospholipases; D010738:Type C Phospholipases; D015032:Zinc