Dissociation of enzymatic and pharmacological properties of piratoxins-I and -III, two myotoxic phospholipases A2 from Bothrops pirajai snake venom.
Piratoxins (PrTX) I and III are phospholipases A2 (PLA2s) or PLA2 homologue myotoxins isolated from Bothrops pirajai snake venom, which also induce myonecrosis, bactericidal activity against Escherichia coli, disruption of artificial membranes, and edema. PrTX-III is a catalytically active hemolytic and anticoagulant Asp49 PLA2, while PrTX-I is a Lys49 PLA2 homologue, which is catalytically inactive on artificial substrates, but promotes blockade of neuromuscular transmission. Chemical modifications of His, Lys, Tyr, and Trp residues of PrTX-I and PrTX-III were performed, together with cleavage of the N-terminal octapeptide by CNBr and inhibition by heparin and EDTA. The lethality, bactericidal activity, myotoxicity, neuromuscular effect, edema inducing effect, catalytic and anticoagulant activities, and the liposome-disruptive activity of the modified toxins were evaluated. A complex pattern of functional differences between the modified and native toxins was observed. However, in general, chemical modifications that significantly affected the diverse pharmacological effects of the toxins did not influence catalytic or membrane disrupting activities. Analysis of structural changes by circular dichroism spectroscopy demonstrated significant changes in the secondary structure only in the case of N-terminal octapeptide cleavage. These data indicate that PrTX-I and PrTX-III possess regions other than the catalytic site, which determine their toxic and pharmacological activities.
Soares
A M
AM
Departamento de Bioquímica e Immunologia, Faculdade de Medicina, Universidade de São Paulo, Ribeirão Preto, SP, Brazil.
Andrião-Escarso
S H
SH
Bortoleto
R K
RK
Rodrigues-Simioni
L
L
Arni
R K
RK
Ward
R J
RJ
Gutiérrez
J M
JM
Giglio
J R
JR
D000098:Acetophenones / Q000737:chemistry; D000818:Animals; D001681:Biological Assay; D017837:Bothrops; D002942:Circular Dichroism; D003435:Crotalid Venoms / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D018360:Crystallography, X-Ray; D003488:Cyanogen Bromide / Q000737:chemistry; D003964:Diaphragm / Q000187:drug effects / Q000294:innervation / Q000502:physiology; D004487:Edema / Q000139:chemically induced; D004791:Enzyme Inhibitors / Q000737:chemistry; D054501:Group II Phospholipases A2; D066298:In Vitro Techniques; D008081:Liposomes / Q000737:chemistry / Q000378:metabolism; D008297:Male; D051379:Mice; D008826:Microbial Sensitivity Tests; D009132:Muscles / Q000187:drug effects*; D009578:Nitrobenzenes / Q000737:chemistry; D009195:Peroxidase / Q000032:analysis; D010741:Phospholipases A / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology*; D054467:Phospholipases A2; D017433:Protein Structure, Secondary; D030162:Reptilian Proteins; D017386:Sequence Homology, Amino Acid; D013329:Structure-Activity Relationship
C427238:2-nitrobenzenesulfonyl fluoride; D000098:Acetophenones; D003435:Crotalid Venoms; D004791:Enzyme Inhibitors; D008081:Liposomes; D009578:Nitrobenzenes; D030162:Reptilian Proteins; C002732:2-nitrobenzenesulfenyl chloride; D009195:Peroxidase; C114085:piratoxin I; D010741:Phospholipases A; D054501:Group II Phospholipases A2; D054467:Phospholipases A2; C120516:piratoxin III; D003488:Cyanogen Bromide; C006821:4-bromophenacyl bromide