title: PhTX-II a basic myotoxic phospholipase A₂ from Porthidium hyoprora snake venom, pharmacological characterization and amino acid sequence by mass spectrometry.
abstract: A monomeric basic PLA₂ (PhTX-II) of 14149.08 Da molecular weight was purified to homogeneity from Porthidium hyoprora venom. Amino acid sequence by in tandem mass spectrometry revealed that PhTX-II belongs to Asp49 PLA₂ enzyme class and displays conserved domains as the catalytic network, Ca²⁺-binding loop and the hydrophobic channel of access to the catalytic site, reflected in the high catalytic activity displayed by the enzyme. Moreover, PhTX-II PLA₂ showed an allosteric behavior and its enzymatic activity was dependent on Ca²⁺. Examination of PhTX-II PLA₂ by CD spectroscopy indicated a high content of alpha-helical structures, similar to the known structure of secreted phospholipase IIA group suggesting a similar folding. PhTX-II PLA₂ causes neuromuscular blockade in avian neuromuscular preparations with a significant direct action on skeletal muscle function, as well as, induced local edema and myotoxicity, in mice. The treatment of PhTX-II by BPB resulted in complete loss of their catalytic activity that was accompanied by loss of their edematogenic effect. On the other hand, enzymatic activity of PhTX-II contributes to this neuromuscular blockade and local myotoxicity is dependent not only on enzymatic activity. These results show that PhTX-II is a myotoxic Asp49 PLA₂ that contributes with toxic actions caused by P. hyoprora venom.
authors.affiliation: Department of Biochemistry, Institute of Biology, State University of Campinas (UNICAMP), P.O. Box 6109, 13083-970 Campinas, SP, Brazil. salomonhv77@yahoo.com.br.
authors.forename: Salomón
authors.initials: S
authors.lastname: Huancahuire-Vega
authors.affiliation: Department of Biochemistry, Institute of Biology, State University of Campinas (UNICAMP), P.O. Box 6109, 13083-970 Campinas, SP, Brazil. poncesoto@yahoo.com.ar.
authors.forename: Luis Alberto
authors.initials: LA
authors.lastname: Ponce-Soto
authors.affiliation: Department of Biochemistry, Institute of Biology, State University of Campinas (UNICAMP), P.O. Box 6109, 13083-970 Campinas, SP, Brazil. marango@unicamp.br.
authors.forename: Sergio
authors.initials: S
authors.lastname: Marangoni
mesh_terms: D000098:Acetophenones / Q000627:therapeutic use; D000595:Amino Acid Sequence; D000818:Animals; D065096:Calcium Chelating Agents / Q000494:pharmacology; D020134:Catalytic Domain; D002645:Chickens; D017124:Conserved Sequence; D003435:Crotalid Venoms / Q000037:antagonists & inhibitors / Q000201:enzymology* / Q000633:toxicity; D004195:Disease Models, Animal; D004487:Edema / Q000209:etiology / Q000517:prevention & control; D004791:Enzyme Inhibitors / Q000494:pharmacology / Q000627:therapeutic use; D054501:Group II Phospholipases A2 / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism / Q000633:toxicity*; D066298:In Vitro Techniques; D051379:Mice; D008969:Molecular Sequence Data; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000473:pathology / Q000503:physiopathology; D009220:Myositis / Q000209:etiology* / Q000517:prevention & control; D009498:Neurotoxins / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000302:isolation & purification / Q000633:toxicity*; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D012909:Snake Bites / Q000188:drug therapy / Q000473:pathology / Q000503:physiopathology*; D017819:Viperidae
chemical_list: D000098:Acetophenones; D065096:Calcium Chelating Agents; D003435:Crotalid Venoms; D004791:Enzyme Inhibitors; D009498:Neurotoxins; D054501:Group II Phospholipases A2; C006821:4-bromophenacyl bromide