I haven't been able to get this question answered through the internet so far, so I was looking for a more professional angle in which this question can be answered.
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9$\begingroup$ Snake venom is almost entirely made up of proteins...thousand of different proteins, which means thousands of different chemical formulae. $\endgroup$– airhuffCommented Apr 15, 2017 at 6:17
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$\begingroup$ In cobras its a protein unimaginatively its called cobratoxin. (You can see x-ray structures on web). The active site has been studied and shown (by time resolved fluorescence; it has a singe trp) to be rather rigid and by being so mimics the geometry of curare type molecules. $\endgroup$– porphyrinCommented Apr 15, 2017 at 9:38
3 Answers
There are several kinds of snake venom, and as far as I know they are all complex enzymes: it means that they are complex macromolecules, made by amminoacids (these, "small molecules") bound with peptide bonds. For enzymes and proteins, the chemical nomenclature is quite impratical: it's way easier to define the enzyme by giving the names of the amminoacid chain it's made of. For instance, for crotamine the amminoacid sequence is: YKQCHKKGGHCFPKEKICLPPSSDFGKMDCRWRWKCCKKGS—G
The wikipedia article of snake venom clearly defines the composition of snake venom. To prevent being a wall of text, I arranged them in points and bolded the chemicals.
Proteins constitute 90-95% of venom's dry weight and they are responsible for almost all of its biological effects. Proteins are toxins, neurotoxins in particular, as well as nontoxic proteins (which also have pharmacological properties),
Enzymes (molecular weight 13-150 KDa) make-up 80-90% of viperid and 25-70% of elapid venoms: digestive hydrolases, L-amino acid oxidase, phospholipases, thrombin-like pro-coagulant, and kallikrein-like serine proteases and metalloproteinases (hemorrhagins), which damage vascular endothelium.
Polypeptide toxins (molecular weight 5-10 KDa) include cytotoxins, cardiotoxins, and postsynaptic neurotoxins (such as α-bungarotoxin and α-Cobratoxin), which bind to acetylcholine receptors at neuromuscular junctions.
Compounds with low molecular weight (up to 1.5 KDa) include metals, peptides, lipids, nucleosides, carbohydrates, amines, and oligopeptides, which inhibit angiotensin converting enzyme (ACE) and potentiate bradykinin (BPP). Inter- and intra-species variation in venom chemical composition is geographical and ontogenic.
Phosphodiesterases interfere with the prey's cardiac system, mainly to lower the blood pressure.
Phospholipase A2 causes hemolysis by lysing the phospholipid cell membranes of red blood cells.
Amino acid oxidases and proteases are used for digestion. They also triggers some other enzymes and is responsible for the yellow colour of the venom of some species.
Hyaluronidase increases tissue permeability to accelerate absorption of other enzymes into tissues.
Some snake venoms carry fasciculins, like the mambas (Dendroaspis), which inhibit cholinesterase to make the prey lose muscle control.
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$\begingroup$ While I appreciate this answer, the list format that was necessarily adopted, as well as the inevitable brevity of each entry, make me doubt the usefulness of the question. $\endgroup$ Commented Apr 15, 2017 at 19:01
Snake Venom is a mixture of chemical compounds. It certainly doesn't have "a chemical formula". Your question is similar to one asking "What is the color of a car?" Just like cars come in a wide range of colors, venoms have a wide variety of recipes (mixtures) and even snakes of the same species may have different compositions of their venoms. More details are easily available, and easily found on-line. For example: https://en.wikipedia.org/wiki/Snake_venom and https://en.wikipedia.org/wiki/Venom#Snakes. For more specific information, you should A. Determine the formal taxonomic name of the species you are interested in and then B. Use Google Scholar or some other search engine which includes the academic literature. Many of these articles won't be satisfactory, I'd guess, because they generally address specific ingredients of the "witch's brew". But you'll most likely find some older articles which are broader. (Many of which will be behind pay-walls, unfortunately. You may have to visit the nearest public university for "free" access.