PHOSPHOLIPASE A2 FROM Lachesis muta (BUSHMASTER) SNAKE VENOM:BIOCHEMICAL CHARACTERIZATION AND EFFECTS ON PLATELET AGGREGATION

Mini-Symposium - Abstracts

14 PHOSPHOLIPASE A2 FROM Lachesis muta (BUSHMASTER) SNAKE VENOM: BIOCHEMICAL CHARACTERIZATION AND EFFECTS ON PLATELET AGGREGATION

A.L. FULY , O.L.T. MACHADO , E.W. ALVES , C.R. CARLINI

Department of Medical Biochemistry, Federal University of Rio de Janeiro and Laboratory of Proteins and Peptides, State University of the Northern Rio de Janeiro, Campos, RJ, Brazil

Snake venoms are rich sources of Phospholipases A2(PLA2) enzymes (EC 3.1.1.4.) which induce a wide range of pharmacological activities, including neurotoxic, cardiotoxic, myotoxic, anticoagulant and hemorrhagic effects. Many of these enzymes interfere with the primary homeostasis, either as activators or inhibitors of platelet functions. The molecular basis for the enzyme effects on platelets is still in most cases poorly understood. Hydrolysis of membrane phospholipids and/or plasma lipoproteins is often involved in the effects PLA2 enzymes cause on platelets. In some cases, however, the pharmacological effects of the protein were found to be dissociated from its enzymatic activity.

Lachesis muta (Bushmaster or surucucu), the longest of all venomous snakes, is found in the tropical rain forest of Central and South America, including Brazil. Despite the severity of the symptoms that follow the bite such as intense local pain and edema, hemorrhage, hypotension, convulsions, little is known about the venom composition. A phospholipase A2, denoted LM-PLA2 was purified from L. muta venom and presented a single polypeptide chain with an isoelectric point of 4.7 and apparent molecular weight of 17-18 kDa. The partial aminoacid sequence indicated a high degree of homology for LM-PLA2 and others PLA2 from different sources.

Collagen-induced aggregation of rabbit platelets was strongly inhibited by LM-PLA2, this effect being dependent on the hydrolysis of plasma phospholipids and/or lipoproteins, most probably those rich in phosphatidylcholine. LM-PLA2 also moderately inhibited aggregation of rabbit platelets induced by low levels of ADP, thrombin and arachidonate The enzymatic activity as well as the pharmacological effects on platelets was abolished by treating the protein with p-bromophenacyl bromide or 2-mercapto-ethanol. Thermal inactivation also affected both parameters in parallel, thus suggesting that these biological properties are correlated and belong to a the same protein molecule.

CORRESPONDENCE TO:

Dra. Celia Regina R. S. Carlini - Departamento de Bioquímica, UFRJ, CCS/Bloco H, 2º andar, Ilha do Fundão, CEP 21910-914, Rio de Janeiro, RJ, Brasil. email: [e-mail]

Publication Dates

• Publication in this collection
  08 Jan 1999
• Date of issue
  1997