title: Exploring and understanding the functional role, and biochemical and structural characteristics of an acidic phospholipase A2,AplTx-I, purified from Agkistrodon piscivorus leucostoma snake venom.
abstract: Phospholipases A2(PLA2s) constitute a class of extensively studied toxins, isolated from snake venoms. Basic PLA2isoforms mediate various toxicological effects, while the acidic isoforms generally have higher enzymatic activities, but do not promote evident toxic effects. The functions of these acidic isoforms in snake venoms are still not completely understood and more studies are needed to characterize the biological functions and diversification of acidic toxins in order to justify their abundant presence in these secretions. Recently, Lomonte and collaborators demonstrated, in a proteomic and toxicological study, high concentrations of PLA2s in the venom of Agkistrodon piscivorus leucostoma. We have, herein, purified and characterized an acidic PLA2from this snake venom, denominated AplTx-I, in order to better understand its biochemical and structural characteristics, as well as its biological effects. AplTx-I was purified using two chromatographic steps, in association with enzymatic and biological assays. The acidic toxin was found to be one of the most abundant proteins in the venom of A. p. leucostoma; the protein was monomeric with a molecular mass of 13,885.8 Da, as identified by mass spectrometry ESI-TOF and electrophoresis. The toxin has similar primary and tridimensional structures to those of other acidic PLA2s, a theoretical and experimental isoelectric point of ≈5.12, and a calcium-dependent enzyme activity of 25.8985 nM/min/mg, with maximum values at 37 °C and pH 8.0. Despite its high enzymatic activity on synthetic substrate, AplTx-I did not induce high or significant myotoxic, coagulant, anticoagulant, edema, neuromuscular toxicity in mouse phrenic nerve-diaphragm preparations or antibacterial activities. Interestingly, AplTx-I triggered a high and selective neuromuscular toxicity in chick biventer cervicis preparations. These findings are relevant to provide a deeper understanding of the pharmacology, role and diversification of acidic phospholipase A2isoforms in snake venoms.
authors.affiliation: Department of Biochemistry and Tissue Biology, Institute of Biology, Campinas State University (UNICAMP), Campinas, SP, Brazil.
authors.forename: L M
authors.initials: LM
authors.lastname: Resende
authors.affiliation: IKIAM - Universidad Regional Amazónica, Km 7 Via Muyuna, Tena, Napo, Ecuador; International Network of Ecuadorian Snakes Venom Studies (RIEVSE), Ecuador. Electronic address: rafael.dealmeida@ikiam.edu.ec.
authors.forename: J R
authors.initials: JR
authors.lastname: Almeida
authors.affiliation: Department of Pharmacology, Faculty of Medical Sciences, State University of Campinas (UNICAMP), Campinas, SP, Brazil.
authors.forename: R
authors.initials: R
authors.lastname: Schezaro-Ramos
authors.affiliation: Department of Pharmacology, Faculty of Medical Sciences, State University of Campinas (UNICAMP), Campinas, SP, Brazil.
authors.forename: R C O
authors.initials: RC
authors.lastname: Collaço
authors.affiliation: Department of Pharmacology, Faculty of Medical Sciences, State University of Campinas (UNICAMP), Campinas, SP, Brazil.
authors.forename: L R
authors.initials: LR
authors.lastname: Simioni
authors.affiliation: Centro de Bioinformática y Simulación Molecular (CBSM), Universidad de Talca, 2 Norte 685, Casilla 721, Talca, Chile.
authors.forename: D
authors.initials: D
authors.lastname: Ramírez
authors.affiliation: Centro de Bioinformática y Simulación Molecular (CBSM), Universidad de Talca, 2 Norte 685, Casilla 721, Talca, Chile; International Network of Ecuadorian Snakes Venom Studies (RIEVSE), Ecuador.
authors.forename: W
authors.initials: W
authors.lastname: González
authors.affiliation: Oswaldo Cruz Foundation (FIOCRUZ), CEBio, Fiocruz Rondônia and Federal University of Rondônia, Porto Velho, RO, Brazil; International Network of Ecuadorian Snakes Venom Studies (RIEVSE), Ecuador.
authors.forename: A M
authors.initials: AM
authors.lastname: Soares
authors.affiliation: Oswaldo Cruz Foundation (FIOCRUZ), CEBio, Fiocruz Rondônia and Federal University of Rondônia, Porto Velho, RO, Brazil; International Network of Ecuadorian Snakes Venom Studies (RIEVSE), Ecuador.
authors.forename: L A
authors.initials: LA
authors.lastname: Calderon
authors.affiliation: Department of Biochemistry and Tissue Biology, Institute of Biology, Campinas State University (UNICAMP), Campinas, SP, Brazil.
authors.forename: S
authors.initials: S
authors.lastname: Marangoni
authors.affiliation: IKIAM - Universidad Regional Amazónica, Km 7 Via Muyuna, Tena, Napo, Ecuador; International Network of Ecuadorian Snakes Venom Studies (RIEVSE), Ecuador.
authors.forename: S L
authors.initials: SL
authors.lastname: da Silva
mesh_terms: D017836:Agkistrodon; D000818:Animals; D002645:Chickens; D003435:Crotalid Venoms / Q000737:chemistry / Q000633:toxicity*; D051379:Mice; D008970:Molecular Weight; D009469:Neuromuscular Junction / Q000187:drug effects / Q000502:physiology; D054467:Phospholipases A2 / Q000737:chemistry / Q000633:toxicity*; D010791:Phrenic Nerve / Q000187:drug effects / Q000502:physiology; D020033:Protein Isoforms; D017208:Rats, Wistar
chemical_list: D003435:Crotalid Venoms; D020033:Protein Isoforms; D054467:Phospholipases A2
keywords: Acidic phospholipase A(2); Agkistrodon piscivorus leucostoma; Pharmacological activity; Snake venom