Chemical modifications of PhTX-I myotoxin from Porthidium hyoprora snake venom: effects on structural, enzymatic, and pharmacological properties.

Salomón Huancahuire-Vega,Luciana M Hollanda,Marcelo Lancellotti,Daniel H A Corrêa,Carlos H I Ramos,Sergio Marangoni,Luis Alberto Ponce-Soto

doi:10.1155/2013/103494

Abstract

We recently described the isolation of a basic PLA2 (PhTX-I) from Porthidium hyoprora snake venom. This toxin exhibits high catalytic activity, induces in vivo myotoxicity, moderates footpad edema, and causes in vitro neuromuscular blockade. Here, we describe the chemical modifications of specific amino acid residues (His, Tyr, Lys, and Trp), performed in PhTX-I, to study their effects on the structural, enzymatic, and pharmacological properties of this myotoxin. After chemical treatment, a single His, 4 Tyr, 7 Lys, and one Trp residues were modified. The secondary structure of the protein remained unchanged as measured by circular dichroism; however other results indicated the critical role played by Lys and Tyr residues in myotoxic, neurotoxic activities and mainly in the cytotoxicity displayed by PhTX-I. His residue and therefore catalytic activity of PhTX-I are relevant for edematogenic, neurotoxic, and myotoxic effects, but not for its cytotoxic activity. This dissociation observed between enzymatic activity and some pharmacological effects suggests that other molecular regions distinct from the catalytic site may also play a role in the toxic activities exerted by this myotoxin. Our observations supported the hypothesis that both the catalytic sites as the hypothetical pharmacological sites are relevant to the pharmacological profile of PhTX-I.

Highlights

Phospholipase A2 (PLA2; EC 3.1.1.4) enzymes catalyse the hydrolysis of acyl ester bond of 1,2-diacyl-3-sn-phosphoglycerides at the sn-2 position, with a requirement for a Ca2+ [1]
We recently described the isolation of a basic PLA2 (PhTX-I) from Porthidium hyoprora snake venom. is toxin exhibits high catalytic activity, induces in vivo myotoxicity, moderates footpad edema, and causes in vitro neuromuscular blockade
A er chemical treatment, a single His, 4 Tyr, 7 Lys, and one Trp residues were modi ed. e secondary structure of the protein remained unchanged as measured by circular dichroism; other results indicated the critical role played by Lys and Tyr residues in myotoxic, neurotoxic activities and mainly in the cytotoxicity displayed by PhTX-I

Summary

Introduction

Phospholipase A2 (PLA2; EC 3.1.1.4) enzymes catalyse the hydrolysis of acyl ester bond of 1,2-diacyl-3-sn-phosphoglycerides at the sn-2 position, with a requirement for a Ca2+ [1]. Within the family Viperidae, two distinct types of venom PLA2 molecules have been described, all of them sharing a high degree of homology both in primary and threedimensional structure [13]: the “classical” PLA2, that present an invariant Asp residue that plays a key role in catalysis; and the “PLA2 homologues,” devoid of enzymatic activity, that present the substitution of Asp by Lys or, less frequently, by Ser, Arg, Gln, or Asn [14, 15] Despite their difference in catalysis, both the Asp and the Lys proteins are BioMed Research International able to induce various pharmacological effects [16]. A site close to the C-terminus, comprising a variable combination of basic and hydrophobic amino acids, has been identi ed as being responsible for toxicity [19]

Methods

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Discussion

Conclusion