title: Phospholipase C from Pseudomonas aeruginosa and Bacillus cereus; characterization of catalytic activity.
abstract: OBJECTIVE
  To study characteristics of phospholipases C (PLCs), their importance for producing microorganisms as well as the potential of their use for industrial purposes.
  
  
  METHODS
  PLC from Bacillus cereus (B. cereus) D101 was selected as an example of Gram-positive PLCs and PLC from Pseudomonas aeruginosa (P. aeruginosa) D183 of Gram-negative ones. Enzymes were partially purified by ammonium sulfate precipitation followed by membrane dialysis. Partially purified preparations were used to study effect of different factors on activities as well as in substrate specificity tests which were conducted using a turbidimetric assay method.
  
  
  RESULTS
  Maximum activity was at pH 7 and 8 and 40 °C for P. aeruginosa PLC, and pH 8-10 and 37 °C for B. cereus PLC. Both PLCs were inhibited by Pi at 5 mM or higher, whereas, PLC from B. cereus only was inhibited by EDTA. Activity of P. aeruginosa PLC was not affected by removing Zn(2+) ions from reaction mixture or their replacement with Ca(2+), Ba(2+), Mg(2+) or Mn(2+) ions. Vis-à-vis, activity of B. cereus PLC was found to be metal ion dependent. PLCs from both isolates were relatively thermostable and showed maximum affinity toward phosphatidylcholine. Sphingomyelin and phosphatidylethanolamine were not good substrates and phosphatidylinositol, phosphatidylserine, phosphatidylglycerol and cardiolipin could be considered non-substrates.
  
  
  CONCLUSIONS
  Human body physiological conditions could favor activity of P. aeruginosa and B. cereus PLCs. These enzymes may participate in phosphate scavenging and virulence of producing isolates but not in autolysis. PLCs from both isolates are potential candidates for industrial use.
authors.affiliation: Department of Microbiology and Immunology, Faculty of Pharmacy, Ain Shams University, Cairo, Egypt.
authors.forename: Nooran Sherif
authors.initials: NS
authors.lastname: Elleboudy
authors.affiliation: Department of Microbiology and Immunology, Faculty of Pharmacy, Ain Shams University, Cairo, Egypt. Electronic address: maboulwafa@yahoo.com.
authors.forename: Mohammad Mabrouk
authors.initials: MM
authors.lastname: Aboulwafa
authors.affiliation: Department of Microbiology and Immunology, Faculty of Pharmacy, Ain Shams University, Cairo, Egypt.
authors.forename: Nadia Abdel-Haleem
authors.initials: NA
authors.lastname: Hassouna
keywords: Bacillus cereus; Catalytic activity; Phospholipase C; Pseudomonas aeruginosa; Substrate specificity