Mass spectrometry analysis, amino acid sequence and biological activity of venom components from the Brazilian scorpion Opisthacanthus cayaporum.

This communication reports the separation of 80 fractions from the venom of the Ischnuridae scorpion Opisthacanthus cayaporum by high-performance liquid chromatography (HPLC). From these, 93 distinct components were identified by liquid chromatography/electrospray mass spectrometry (LC/ESI-MS) analysis, with molecular weights varying from 229.2 to 61,144.0 atomic mass units. Additionally, the HPLC fractions were analyzed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) which resulted in 221 distinct components, among which were 52 of the 93 obtained by LC/ESI-MS. The entire set of different molecular species found (total of 262 molecular masses) has a trimodal molecular weight distribution, with 42% of the components possessing 229.2-2985.3Da, 37% within the range of 3045.0-7258.6Da and 12% within the range 7458.4-9429Da. Seventeen peptides/proteins were isolated and were sequenced by Edman degradation, among which were a scorpine-like peptide (8315Da), presenting antimicrobial activity, and two phospholipase A2 with a molecular weight around 14kDa. The pharmacological effects of the venom were tested on isolated rat and insect (cockroach) nerves using the single sucrose-gap assay. The ED50 of the venom was 1.1mg/ml in insect nerves. Venom concentrations in the order of 3mg/ml causes only 9% reduction of compound action potentials (APs) of rat nerves, suggesting that this venom is rather specific for insects. Comparative analysis of venom from male and female O. cayaporum was performed by HPLC and MALDI-TOF-MS showing no qualitative variations, but rather quantitative differences among both samples.