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BioMed Research International
Volume 2013 (2013), Article ID 103494, 12 pages
Research Article

Chemical Modifications of PhTX-I Myotoxin from Porthidium hyoprora Snake Venom: Effects on Structural, Enzymatic, and Pharmacological Properties

1Department of Biochemistry, Institute of Biology, State University of Campinas (UNICAMP), P.O. Box 6109, 13083-970 Campinas, SP, Brazil
2Department of Organic Chemistry, Institute of Chemistry, University of Campinas (UNICAMP), Campinas, SP, Brazil
3Biotechnology Laboratory (LABIOTEC), Department of Biochemistry, Institute of Biology, University of Campinas (UNICAMP), Campinas, SP, Brazil
4National Institute of Science and Technology for Structural Biology and Bioimaging, Rio de Janeiro, RJ, Brazil

Received 17 September 2012; Accepted 31 October 2012

Academic Editor: Elen Cristina Teizem Landucci

Copyright © 2013 Salomón Huancahuire-Vega et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


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.