The liberation movement

Weizmann Institute scientists used the technique of accelerated evolution and developed an enzyme that provides protection against nerve gas

Defense against a nerve gas attack is currently a significant component of the defense system of many countries in the world. The nerve gases are used by armies and terrorist organizations, and are both a military and civilian threat, but the existing medicinal solutions against them are only partial. A multidisciplinary team of scientists from the Weizmann Institute of Science succeeded in developing an enzyme that breaks down the nerve gas effectively, even before it could cause damage to the nerves and muscles. The research findings were recently published in the scientific journal Nature Chemical Biology. Experiments carried out recently at the US Army laboratories (USAMRICD) showed that injecting a relatively small amount of the enzyme into animals provides protection against various types of nerve gases, against which until now there was no effective protection.
The nerve gases disrupt the transmission of messages from the nerve cells to the muscle cells, and cause the loss of control over the muscles - which ultimately leads to death by suffocation. The gas interferes with the activity of acetylcholinesterase, the enzyme responsible for breaking down the neurotransmitter acetylcholine. As a result, the acetylcholine works non-stop, which is manifested in the constant contraction of all the muscles in the body. Today there are several drugs used to treat cases of nerve gas poisoning. These drugs may be effective in exposure to small doses of gas, but do not provide protection against high doses, are ineffective against all types of nerve gases, and cause severe side effects. They are also unable to repair the brain and motor damage caused by the nerve gas, or prevent it.

An ideal solution to the problem is to capture and break down the nerve gas using enzymes even before it binds to acetylcholine esterase, thus preventing the damage in advance. The main obstacle facing the realization of this idea is the fact that nerve gases are man-made substances, and therefore, during evolution, no natural enzymes have developed that recognize and break them down. In the past, scientists in various parts of the world were able to identify enzymes capable of breaking down similar substances, but these enzymes were characterized by little efficiency, so that a very large amount of the enzyme was required to break down the nerve gas. The need for these quantities made the use of these enzymes impractical.
This is where Prof. Dan Toufik from the Department of Biological Chemistry at the Weizmann Institute of Science enters the picture. He developed a special method for genetic engineering of enzymes, which allowed him and his research partners to overcome the obstacle. The research group led by Prof. Toufik performed an accelerated evolutionary process on enzymes in vitro, in the framework of which a "natural selection" of enzymes with certain properties takes place under artificial "evolutionary pressure". The method is based on causing many mutations in the enzyme, and scanning the variety of versions created, with the aim of finding the mutant enzymes that demonstrate higher efficiency in breaking down nerve gas. These improved enzymes go through another round of mutations, and God forbid. In previous studies Prof. Toufik showed that in this way it is possible to improve the efficiency of enzymes by hundreds or even thousands of meters.
For the purpose of the current task, Prof. Toufik chose an enzyme that has been extensively studied in his laboratory, called PON1. The main function of the enzyme, found naturally in the human body, is to break down oxidation products of fats that accumulate on the walls of blood vessels, thus preventing atherosclerosis. At the same time, he also randomly performs a small "haltura" - breaking down substances belonging to the nerve gas family. This activity was not nurtured by evolution, so its efficiency remains very low. This is precisely where the in vitro evolution method came into play, by means of which the scientists hoped to reach a situation where the "haltoristic" activity of the enzyme becomes a main task performed quickly and efficiently.
In the first step, Prof. Toufik and his group members - including research associate Dr. Moshe Goldschmidt and post-doctoral researcher Dr. Rinko Devi Gupta - proceeded to induce mutations in the PON1 enzyme, some of which were random, and some of which targeted the key sites of the enzyme. To identify the effective mutants, the scientists teamed up with Dr. Yaakov Eshani, from the department of structural biology at the institute. The scanning method they developed mimics what happens in reality, in the body, after exposure to nerve gas: they placed the acetylcholine esterase in a test tube together with a mutant PON1 enzyme they wanted to test, and added a small amount of nerve gas. In the case where the acetylcholine esterase continues to work normally, it can be concluded that the enzyme successfully decomposed the nerve gas, before damage to the acetylcholine esterase occurred. The researchers concentrated on two types of nerve gases, soman and cycloserine, both because of their high toxicity, and because the current treatment (atropine and 2PAM) is not effective at all against cycloserine.

After several rounds of mutations and scans, the scientists managed to get active mutant enzymes, which manage to break down nerve gas efficiently, before any damage is done to the acetylcholine esterase enzyme. A team of scientists from the Department of Structural Biology, which included Prof. Yoel Sussman, Prof. Israel Silman, and research student Moshe Ben David, analyzed the structure of these enzymes. In experiments carried out in US Army laboratories, it was found that the enzymes provide animals with full protection against two types of nerve gas, even in high doses of gas, when they are given as preventive treatment, before exposure.
Prof. Toufik says that the new development arouses many expectations and hopes. In the future, the scientists plan to expand the scope and develop a preventative treatment that provides protection against all types of nerve gases that exist. In addition, they will try to develop enzymes with high enough efficiency to break down the nerve gas even after the exposure.
air peaks

About two years ago, following the repeated requests of his son - an avid mountain climber - Prof. Dan Tofik found himself "carrying his old bones", according to him, to the top of Jebel Ram in Jordan. Toufik fell in love with the mountains, and since that adventure he occasionally goes out to conquer peaks in Israel, Jordan, and also in Europe and the USA, accompanied by his son, his group members and friends. "In mountaineering, as in science, reaching the top opens up the horizon and reveals the existence of new peaks," he says. In the photo, Prof. Tawfik and his friend Hanina Kali, the mountain climbing guide, are seen on the summit of Jebel Umm-Asharin (1,750 meters above sea level), near Wadi Ram, in southern Jordan.