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. Method: 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
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.@*METHOD@#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.@*CONCLUSION@#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.
ABSTRACT
This study was conducted to investigate the protective effect of thymus extract against peptic ulcer in stress-induced gastric ulcer model in rats, together with the determination of its effect on gastric secretion. The possible effect of thymus extract on the isolated fundal strip of rat stomach and the isolated smooth muscle of guinea pig ileum was also studied. The oral administration of thymus extract [50 mg/kg/day] for one week significantly reduced the incidence of ulceration, the mean ulcer score and the ulcer index compared with the saline control group and achieved a preventive index of 57%. Also, it decreased gastric acidity, as it significantly reduced the mean pepsin concentration as compared with the saline control animals. On the other hand, thymus extract produced a dose- dependent relaxant effect on the isolated smooth muscle of guinea pig ileum, but not the isolated fundal strip of rat stomach