Siamensis Venom Research Articles

Phospholipase A inhibition of acetylcholine receptor function in [formula omitted] membrane vesicles

A protein isolated from Naja naja siamensis venom on the basis of its phospholipase A activity inhibits acetylcholine receptor function in post-synaptic membrane vesicles from Torpedo californica . Specifically, the phospholipase A prevents the large increase in sodium efflux that can normally be induced by carbamylcholine, a receptor agonist. The phospholipase A inhibition shows the following properties: 1) it occurs at concentrations 50 times lower than the concentrations required for inhibition by α-neurotoxins; 2) the phospholipase A has no effect on the binding properties of the receptor; 3) the inhibition is abolished by removal of calcium ions; and 4) some phospholipid hydrolysis accompanies inhibition. It is suggested that the phospholipase A acts enzymatically to uncouple ligand binding from ion permeability in the receptor containing membrane vesicles.

Sensitivity of cultured embryonic heart cells to cardiotoxin obtained from Naja naja siamensis venom

Clumps of embryonic chick heart cells in culture were exposed to cardiotoxin prepared by Sephadex CM-50 fractionation from snake (Naja naja siamensis) venom. Cardiotoxin irreversibly depolarized these cells. More of the cells cultured from 4-day embryos, than from 12–13-day embryos, continued to beat spontaneously after 30 min exposure to the toxin at a concentration of 15–20 μg per ml.

Isolation of the principal neurotoxins of two Naja naja subspecies.

The principal neurotoxins of two commercial (Miami Serpentarium) preparations of venom from Naja naja siamensis, or Thailand cobra, and Naja naja naja, or spectacled Indian cobra, are isolated rapidly and simply by ion exchange chromatography on short (20–30 cm) columns of Bio-Rex 70 (or IRC-50) in volatile ammonium acetate buffers, followed by gel filtration on Sephadex G-50. The Naja naja siamensis preparation contains a single principal neurotoxin that accounts for about one-fourth of the weight of the lyophilized crude venom, or one-third of the total venom protein. The Naja naja naja venom preparation contains approximately equal amounts of two principal neurotoxins which together account for more than one-fourth of the total venom protein. The three principal neurotoxins contain 71 amino acids in a single peptide chain cross-linked by five disulfide bridges. The two Naja naja naja neurotoxins appear to differ only by a serine/isoleucine substitution, while both appear to differ from the principal Naja naja siamensis toxin only by two additional replacements: arginine for lysine and glycine for alanine. Three minor neurotoxic components that are present at levels of 1% or less in the Naja naja siamensis venom are also described. One of these is a 61 amino acid toxin containing four disulfide bridges and two residues of tryptophan. The other two contain 62 amino acids and four disulfide bridges. One of the latter toxins appears to be nearly identical to the cobrotoxin of Naja naja atra venom.

Comparison of Naja naja siamensis and Naja naja atra venoms

The immunological properties of Formosan cobra ( Naja naja atra) and Thailand cobra ( Naja n. siamensis) venoms were compared using horse serum antivenin prepared from Thailand cobra venom. Both venoms showed very similar precipitin patterns with immunodiffusion or immunoelectrophoresis on agar gel. Results of polyacetate electrophoresis also indicated that the protein fractions of these two venoms were similar, although they are not identical. Thailand cobra antivenin neutralized the lethal effect in mice of Formosan and Thailand cobra venoms to a similar degree.