Question: In South Korea, pufferfish is famous, and people eat it frequently. However, I have heard that due to the extremely strong poison from the fish, pufferfish is very dangerous to eaters when the chef is not trained well enough to prepare it. Therefore, only licensed chefs certified by the government can cook pufferfish. My question is, what kind of poison comes from the fish and how does it affect our body?
Answer: A pufferfish has tetrodotoxin (TTX), which is a very strong poison found almost everywhere inside its body, such as blood, skin, liver, eyes, and ovaries. As a measure of its potency, tetrodotoxin is much stronger than potassium cyanide, and the poison from only one fish can lead to serious damage to more than thirty people (Figure 1).
When the poison comes into human body, it blocks the sodium channels in the cell membrane, therefore restricting the flow of sodium ions. More specifically, tetrodotoxin binds to the sodium channel due to ionic interactions between positive charge of guanine group of TTX and negative charge carboxylate group of the sodium channel (Hannon& Anslyn, 1993). As a result of this sodium channel block, conduction throughout body and brain is diminished. This lack of nerve impulses causes paralysis in the muscles, asphyxiation, and ultimately leads to coma. If a patient is not treated within four to six hours, he/she will die; there is no treatment for TTX poisoning because it is absorbed very quickly into our body.
Then, how can pufferfish survive even though they have this strong poison within their own body? The answer to this interesting question is that TTX is not toxic to its host. The host has Na+ channel contain a mutation that alters its amino acid sequence and makes it unable to bind TTX (Dudley, et al, 1995). Interestingly, TTX has its pros and cons. In neuroscience, much research has been done to investigate a potential role for TTX as future neuropathic pain reliever.
People might be curious about why people would try to eat such a dangerous fish (Figure 2). Honestly, I have not tried it before but my father said that this is a taste of heaven. If you are a brave person, I highly recommend trying to eat pufferfish foods.
- Deok Yong K.
- Christine L. Hannon and Eric V. Anslyn (1993) The guanidinium group: its biological role and synthetic analogs, Bioorganic Chemistry Frontiers, 12(3):193-255
- S C Dudley, Jr, H Todt, G Lipkind, and H A Fozzard (1995) A mu-conotoxin-insensitive Na+ channel mutant: possible localization of a binding site at the outer vestibule, Biophysical Journal, 69(5): 1657-1665.
- Why are Puffer Fish Poisonous? Tetrodotoxin, TTX (2015) The Science Majors Science Channel, Web: https://www.youtube.com/watch?v=609nhlhM-J4
- Three web sources: