title: Biochemical and monolayer characterization of Tunisian snake venom phospholipases.
abstract: The present study investigated the kinetic and interfacial properties of two secreted phospholipases isolated from Tunisian vipers'venoms: Cerastes cerastes (CC-PLA2) and Macrovipera lebetina transmediterranea (MVL-PLA2). Results show that these enzymes have great different abilities to bind and hydrolyse phospholipids. Using egg-yolk emulsions as substrate at pH 8, we found that MVL-PLA2 has a specific activity of 1473U/mg at 37°C in presence of 1mM CaCl2. Furthermore the interfacial kinetic and binding data indicate that MVL-PLA2 has a preference to the zwitterionic phosphatidylcholine monolayers (PC). Conversely, CC-PLA2 was found to be able to hydrolyse preferentially negatively charged head group phospholipids (PG and PS) and exhibits a specific activity 9 times more important (13333U/mg at 60°C in presence of 3mM CaCl2). Molecular models of both CC-PLA2 and MVL-PLA2 3D structures have been built and their electrostatic potentials surfaces have been calculated. A marked anisotropy of the overall electrostatic charge distribution leads to a significantly difference in the dipole moment intensity between the two enzymes explaining the great differences in catalytic and binding properties, which seems to be governed by the electrostatic and hydrophobic forces operative at the surface of the two phospholipases.
authors.affiliation: Institut Pasteur de Tunis, Laboratoire des Venins et Biomolécules Thérapeutiques LR11IPT08, 13, Place Pasteur, BP 74, 1002 Tunis-Belvédère, Tunisia; Université de Tunis El Manar, Tunisia.
authors.forename: Douja
authors.initials: D
authors.lastname: Baîram
authors.affiliation: Laboratoire de Biochimie et de Génie Enzymatique des Lipases, Ecole Nationale d'Ingénieurs de Sfax (ENIS), Route de Soukra, BP 1173, 3038 Sfax, Tunisia; Université de Sfax, Tunisia.
authors.forename: Imen
authors.initials: I
authors.lastname: Aissa
authors.affiliation: Laboratoire de Biochimie et de Génie Enzymatique des Lipases, Ecole Nationale d'Ingénieurs de Sfax (ENIS), Route de Soukra, BP 1173, 3038 Sfax, Tunisia; Université de Sfax, Tunisia.
authors.forename: Hanen
authors.initials: H
authors.lastname: Louati
authors.affiliation: Institut Pasteur de Tunis, Laboratoire des Venins et Biomolécules Thérapeutiques LR11IPT08, 13, Place Pasteur, BP 74, 1002 Tunis-Belvédère, Tunisia; Université de Tunis El Manar, Tunisia.
authors.forename: Houcemeddine
authors.initials: H
authors.lastname: Othman
authors.affiliation: Institut Pasteur de Tunis, Laboratoire des Venins et Biomolécules Thérapeutiques LR11IPT08, 13, Place Pasteur, BP 74, 1002 Tunis-Belvédère, Tunisia; Université de Tunis El Manar, Tunisia.
authors.forename: Zaineb
authors.initials: Z
authors.lastname: Abdelkafi-Koubaa
authors.affiliation: Laboratoire de Biochimie et de Génie Enzymatique des Lipases, Ecole Nationale d'Ingénieurs de Sfax (ENIS), Route de Soukra, BP 1173, 3038 Sfax, Tunisia; Université de Sfax, Tunisia.
authors.forename: Najeh
authors.initials: N
authors.lastname: Krayem
authors.affiliation: Institut Pasteur de Tunis, Laboratoire des Venins et Biomolécules Thérapeutiques LR11IPT08, 13, Place Pasteur, BP 74, 1002 Tunis-Belvédère, Tunisia; Université de Tunis El Manar, Tunisia.
authors.forename: Mohamed
authors.initials: M
authors.lastname: El Ayeb
authors.affiliation: Institut Pasteur de Tunis, Laboratoire des Venins et Biomolécules Thérapeutiques LR11IPT08, 13, Place Pasteur, BP 74, 1002 Tunis-Belvédère, Tunisia; Université de Tunis El Manar, Tunisia.
authors.forename: Najet
authors.initials: N
authors.lastname: Srairi-Abid
authors.affiliation: Institut Pasteur de Tunis, Laboratoire des Venins et Biomolécules Thérapeutiques LR11IPT08, 13, Place Pasteur, BP 74, 1002 Tunis-Belvédère, Tunisia; Université de Tunis El Manar, Tunisia.
authors.forename: Naziha
authors.initials: N
authors.lastname: Marrakchi
authors.affiliation: Laboratoire de Biochimie et de Génie Enzymatique des Lipases, Ecole Nationale d'Ingénieurs de Sfax (ENIS), Route de Soukra, BP 1173, 3038 Sfax, Tunisia; Université de Sfax, Tunisia. Electronic address: ytgargouri@yahoo.fr.
authors.forename: Youssef
authors.initials: Y
authors.lastname: Gargouri
mesh_terms: D000818:Animals; D006868:Hydrolysis; D007700:Kinetics; D054467:Phospholipases A2 / Q000737:chemistry* / Q000302:isolation & purification; D010743:Phospholipids / Q000737:chemistry*; D014757:Viper Venoms / Q000737:chemistry / Q000201:enzymology*; D017819:Viperidae
chemical_list: D010743:Phospholipids; D014757:Viper Venoms; D054467:Phospholipases A2
keywords: Biochemical characterization; Phospholipase A2; Phospholipid monolayers