There is one important ligand binding site on AChE, which consists of a catalytic triad. The catalytic triad is made up of Serine 203, Histidine 447, and Glutamate 334. The sarin interacts with the AChE enzyme specifically on the active centre of AChE, specifically on the active site of Serine 203 (an amino acid). A phosphonate ester bond is formed, caused by the phosphorylation of serine. The result of this is the formation of an O-P AChE adduct resulting in a P-O bond. This bond is specifically between the oxygen of Ser203 and the phosphorus atom of sarin. This is a covalent bond, and causes the shape of Sarin to change. The creation of this bond is very stable and complicated, and therefore inhibits action of the AChE enzyme. Sarin’s original molecular structure is C4H10FO2P, but once bonded to serine, the CH3CHO side chain is replaced with a negatively charged oxygen, defining the bonded structure.
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