chemistry

Surugatoxin

Surugatoxin is a chemistry topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Surugatoxin rather than just read about it. In short: Surugatoxin (SGTX) is a type of venom found in the mid-gut digestive gland of the Japanese ivory mollusk Babylonia japonica, a carnivorous gastropod. It functions as a ganglionic blocker of nicotinic acetylcholine receptors (nAChRs).

Key takeaways

Surugatoxin belongs to chemistry; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Surugatoxin to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Surugatoxin from memory before moving on to harder problems.

Reference excerpt

Surugatoxin (SGTX) is a type of venom found in the mid-gut digestive gland of the Japanese ivory mollusk Babylonia japonica, a carnivorous gastropod. It functions as a ganglionic blocker of nicotinic acetylcholine receptors (nAChRs). The structurally and functionally related neosurugatoxin, also derived from Babylonia japonica, is an even more potent nAChR antagonist than SGTX. SGTX is a colorless crystalline substance with the chemical formula C25H26BrN5O13 and a molecular weight of 684.4g/mol. Its systematic chemical name is [(2R,3S,5S,6S)-2,3,4,5,6-pentahydroxycyclohexyl] (6aS,7R,8R,9R)-6'-bromo-6a,9-dihydroxy-9-methyl-1,2',3,10-tetraoxo-spiro[4,5,6,7-tetrahydropyrido[1,2-f]pteridine-8,3'-indoline]-7-carboxylate. It is insoluble in organic solvents and has very low solubility in water. The ganglionic blockade of nAChRs by SGTX is similar to that of IS-toxin, a structurally similar compound derived from the same mollusk, Babylonia japonica.

Background and discovery A food poisoning outbreak of 26 cases in the Ganyudo area of Suruga Bay, Shizuoka Prefecture in Japan in September 1965 was traced to ingestion of the toxin surugatoxin (SGTX), named for Suruga Bay. SGTX is contained in the mid-gut digestive gland of the Japanese ivory mollusk, Babylonia japonica, which is used as an ingredient in sushi and sashimi. The food-poisoning patients reported a variety of symptoms, including visual disorders, speech disorders, lazy eye amblyopia, pupil dilation (mydriasis), abdominal distention, dry mouth, numbness of lips, constipation, and vomiting. The toxicity shellfish from the Suruga Bay area varied with time – the toxicity was only present during July through September, when temperatures sometimes reached 25°C and it rapidly declined after 1978, making the availability of surugatoxin and the related substances neosurugatoxin and prosurugatoxin unavailable for research. Kosuge and colleagues found that these toxins are actually the metabolized products of a marine bacterium that belongs to the Coryneform group. Toxicity is a result of bioaccumulation.

Behavioral and physiological effects A number of researchers have characterized the effect of surugatoxin on behavior and physiology in animal models

Mice SGTX causes disturbances in gait, suppression of spontaneous motility, and mydriasis in mice at intravenous (i.v.) dose levels of 0.5-1.0 mg/kg. At higher doses (20–40 mg/kg), intraperitoneal (i.p.) application of SGTX caused depression of respiratory movement and tremor.

Rats SGTX blocks orthodromic transmission, as evidenced by the fact that the synaptic potential is strongly depressed with application of the toxin and the block intensifies as stimulus frequency increases. This effect is slow to develop and is similar to another ganglionic nACHR antagonist, hexamethonium.

Cats SGTX causes depression of spontaneous movement, mydriasis, and relaxation of the nictitating membrane in cats at i.v. dose levels of 0.15-0.2 mg/kg. Further, it produces hypotension of 1–2 hours in duration that is not prevented by treatment with atropine or propranolol.

Humans Most clinical symptoms resulting from Babylonia japonica ingestion, as in the 1965 food-poisoning outbreak, seem to be mediated by ganglion-blockade of nicotinic ACh receptors at various sites; visual impairments and mydriasis due to ciliary ganglion blockade, dry mouth due to submaxillary and otic ganglion blockade, and constipation and abdominal distention due to intestinal intrinsic nerve blockade.

Pharmacology Surugatoxin is a specific, reversible, competitive antagonist of ganglionic nicotinic acetylcholine receptors (nACHRs). Although a number of articles were published in the two decades following the discovery of SGTX in the mid-1960s, relatively little is known about the pharmacological properties of this toxin. Ascher and colleagues posit that ganglionic blockade by SGTX results from binding to the closed state of the channel-receptor complex, possibly to the receptor itself. It is 50-100 times more potent than hexamethonium, another ganglionic antagonist of nAChRs. Brown and colleagues found that the SGTX dissociation constants measured at equilibrium block in rats were 58nM and 76nM, as measured from the shift in depolarization produced by 0.2μM and 2 μM SGTX, respectively. Surugatoxin is listed on two U.S. patents, both for potential clinical treatments. US7468188 proposes the use of locally-administered neurotoxins in the treatment of muscle injury and US7214700 proposes the use of (2-Oxindol-3-ylidenyl) acetic acid derivatives as protein kinase inhibitors. Surugatoxin has not been demonstrated to be effective in either of these treatment proposals, but rather, is listed as a potentially relevant substance in these treatment plans.

References

Illustrations

Worked examples

Example 1 — a first encounter with Surugatoxin

Start with the simplest possible case. Write down what Surugatoxin claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In chemistry, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Surugatoxin before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Surugatoxin ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Surugatoxin

In research: Surugatoxin appears in chemistry research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Surugatoxin in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Surugatoxin is common in secondary-school and first-year university syllabi. It links to neighbouring topics Cyclitol esters, Inositol, Nicotinic antagonists, so understanding it makes those chapters shorter.
In everyday life: Look for Surugatoxin outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Surugatoxin in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Surugatoxin means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Surugatoxin out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Surugatoxin in simple terms?

Why does Surugatoxin matter?

Because it connects several chemistry ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Surugatoxin?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Surugatoxin.