title: Purification, characterization and bactericidal activities of phospholipase A₂ from the dromedary intestine.
abstract: We purified a protein from the dromedary small intestine that displayed potent bactericidal activity against Gram-positive bacteria, and identified it as group-IIA phospholipase A₂ (DrPLA₂-IIA) by NH₂-terminal sequencing and enzymatic measurements. In fact, our findings revealed that the purified PLA₂-IIA was a monomeric protein with a molecular mass of about 14 kDa. Pure enzyme has a specific activity of 329 ± 25 U/mg at optimal conditions (pH 9.5 and 45 °C) in the presence of 6 mM NaDC and 7 mM CaCl₂ with egg yolk emulsion as substrate and binds with a higher affinity to PE than PS and PC. Furthermore, the DrPLA2-IIA activity was dependent on Ca(2+); other cations (Cd(2+), Co(2+), Fe(2+), Mg(2+), Mn(2+), and Zn(2+)) reduced the enzymatic activity notably, suggesting that the arrangement of the catalytic site presents an exclusive structure for Ca(2+). On the other hand, DrPLA2-IIA was highly bactericidal against Gram-positive bacteria with inhibition zones and IC₅₀ values in the range of 21-27 mm and 3.7-8 μg/ml, respectively, whereas Gram-negative bacteria exhibited a much higher resistance. These observations suggest that the main physiological role of DrPLA2-IIA could be the defense of the intestine against bacterial infections.
authors.affiliation: Biochemistry Department, Science College, King Saud University, PO Box 22452, Riyadh 11495, Saudi Arabia. abirghanouchi@yahoo.fr
authors.forename: Abir
authors.initials: A
authors.lastname: Ben Bacha
authors.forename: Sooad K
authors.initials: SK
authors.lastname: Al-Daihan
authors.forename: Hafedh
authors.initials: H
authors.lastname: Mejdoub
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism / Q000494:pharmacology; D001424:Bacterial Infections / Q000201:enzymology; D002162:Camelus; D006094:Gram-Positive Bacteria / Q000254:growth & development*; D007422:Intestines / Q000201:enzymology*; D008670:Metals / Q000737:chemistry / Q000378:metabolism; D054467:Phospholipases A2 / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism / Q000494:pharmacology
chemical_list: D000900:Anti-Bacterial Agents; D008670:Metals; D054467:Phospholipases A2