Atropine blocks a subset of acetylcholine receptors known as muscarinic acetylcholine receptors (mAchRs), so that the buildup of acetylcholine produced by loss of the acetylcholinesterase function has a reduced effect on their target receptor. 2-PAM reactivates the acetylcholinesterase enzyme (AChE), thus reversing the effects of VX. VX and other organophosphates block AChE activity by binding to and covalently inactivating the enzyme via transfer of the phosphonate moiety from VX to the active site of AChE; this inactivates AChE and produces an inactive by-product from the remaining portion of the VX molecule. Pralidoxime (2-PAM) removes this phosphate group.