The Biochemical Terrorist Attacks of Aum Shinrikyo


Aleph/Aum Shinrikyo is a Japanese doomsday cult, whose original leaders have since been executed, responsible for one of the worst domestic terror attacks in Japanese modern history; the Tokyo subway Sarin attack on 20 March 1995. This occurred after their first sarin terrorist attack in 1988, and their several failed acts of bioterrorism involving the poisons VX, botulinum toxin and hydrogen cyanide. [1]

Sarin is an extremely potent man-made nerve agent originally developed as a German pesticide in 1938. Its colourless and odourless nature lead to victims being gradually poisoned unknowingly, after skin contact or ingestion, causing more rapid symptoms when vaporised (after a few seconds) than when in the liquid form (a few minutes to a few hours). Sarin has the highest volatility of all the nerve agents, leading to a high rate of liquid to gas formation.

Several bags containing sarin were punctured and left to attack the nervous systems of the general public during rush hour, resulting in 12 deaths, 50 severe injuries and 1,000 temporary vision problems. Victims reported symptoms immediately after the leaking bags were spotted, leading to vomiting, choking, blinding and paralysis. [1]

The severity of the impacts are influenced by the levels of exposure; mild/moderate levels can lead to complete recovery, whilst high levels propose escalated death risks.

Sarin acts in the same way as organophosphate pesticides by interfering with the nerve signals. When neuromuscular junctions receive electrical impulses, neuron cells release acetylcholine neurotransmitters which attach to receptor muscle cells on the other side of the synapse. This eventually results in muscular contraction. [1]

The enzyme acetylcholinesterase plays a vital role in our nervous system by breaking down the neurotransmitter acetylcholine, producing choline and acetic acid, leading to necessary muscular relaxation. Sarin irreversibly competitively inhibits acetylcholinesterase, leading to an accumulation of acetylcholine at cholinergic receptors. The overstimulation of the nervous system leads to prolonged muscular contraction and eventually, paralysis which, when spreads to the respiratory muscles, causes death. [2]

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Sarin binds with the esteric site, preventing the breakdown of acetylcoline [2]

In previous years, the Japanese cult failed to successfully produce botulinum toxin and hydrogen cyanide; two of the deadliest poisons in the world. Saying this, however, sarin is 500 times more potent than hydrogen cyanide.

Cyanide is commonly found in our daily lives, particularly in the seeds of apricot, almonds, and in cigarette smoke. Due to the regular exposure, our body is able to breakdown small doses of cyanide, leading to little effect, but high doses can prove to be lethal.

The overall role of the mitochondria is to carry out aerobic respiration, creating ATP which our cells use as an energy source; this involves the electron transport chain, which is the last step of the process.

The electron transport chain involves multiple carrier proteins situated on the inner membrane or cytoplasmic membrane of the mitochondria. This process begins when the electron carriers NADH and FADH2 transport hydrogen ions and electrons of substrates from previous processes (eg glycolysis or the citric acid cycle) to other electron carriers (eg cytochromes), ultimately leading to the electron being transported to oxygen. [3]

The pumping of H+ ions across the membrane requires energy, provided by the electrons transported. This leads to an accumulation of positive charge on one side, and a negative charge on the remaining side, creating an electrochemical gradient called a proton motive force (PMF). The H+ ions then diffuse back through the mitochondrial membrane via ATP synthase enzyme complexes, which use the energy from the current of H+ ions to convert ADP to ATP via phosphorylation. [4]

The final electron and hydrogen ion receptor is an oxygen molecule, which is reduced to form a water molecule. Cyanides essentially prevent the oxidative phosphorylation process from occurring by binding to the cytochrome C oxidase enzyme, blocking the electron transport chain from occurring, and halting the reduction of oxygen to water. The electron transport chain is no longer able to continue so ATP is not produced. [5]

Cellular hypoxia (oxygen deprivation), ATP deficiency and metabolic acidosis (overproduction of acid) then occur which can lead to the cessation of vital functions, possibly leading to serious symptoms or death. [6]

What Is Oxidative Phosphorylation? Where Does It Occur?
The electron transport chain initiated by NADH and completed by the reduction of oxygen molecules [6]

Although botulinum toxin has high toxicity (10,000 times that of sarin), it is used in purified, low doses called botox, dysport and xeomin. These all have both cosmetic and medical applications for conditions such as hyperhidrosis, cervical dystonia and a lazy eye.

The effects of botulinum toxin can be presented, on a smaller scale, by the patients of botox procedures. Their wrinkles become smoothened out due to the prevention of muscular contraction, causing prolonged muscular relaxation and decreased fine lines, and the process behind this poison is essentially the opposite of the process behind sarin.

As previously mentioned, the acetylcholine neurotransmitter is produced at neuromuscular junctions before muscular contractions are initiated; this process is controlled by the SNARE complex proteins. Botulinum toxin inhibits these proteins, leading to no acetylcholine being produced, halting muscular contraction. This is only temporary (3-4 months) as the body adapts and produces more neurons, bypassing the botulinum toxin blockage, causing a need for constant top up injections. [7]

When exposed to a high dose flaccid paralysis is caused which, if affecting the respiratory muscles, can be fatal; botulism. [7]

After the sarin attack the leader of the cult, Shoko Asahara, was ordered to pay over ¥1 billion in damages (approx. £7,205,000) to the victims and their families. The cult has now been renamed as ‘Aleph’ and another smaller group, ‘Hikari No Wa’,[1] with reports of around 1,500 members, slowly growing, even after the execution of the leader and 12 members in 2018. This has instigated debate around the death penalty in Japan.


  1. ‘Facts about sarin’, CDC, April 4, 2018
  2. James Hamblin, ‘What Does Sarin Do to People?’, The Atlantic, May 6, 2013
  3. ‘Cyanide fact sheet’, Center for Health Security, December 01, 2013
  4. ‘Cellular respiration’, BBC
  5. Gary Kaiser, ‘Electron transport chain and chemiosmosis’, LibreTexts, Sep 25, 2019
  6. John Staughton, ‘What Is Oxidative Phosphorylation?’, ScienceABC, 6 Dec, 2019
  7. ‘Detailed explanation of how botulinum toxin injections work’, The Dystonia Society


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