Acetylthiocholine: An agent used as a substrate in assays for cholinesterases, especially to discriminate among enzyme types.Acetylcholinesterase: An enzyme that catalyzes the hydrolysis of ACETYLCHOLINE to CHOLINE and acetate. In the CNS, this enzyme plays a role in the function of peripheral neuromuscular junctions. EC N,N',N'',N'''-Tetraisopropylpyrophosphamide. A specific inhibitor of pseudocholinesterases. It is commonly used experimentally to determine whether pseudo- or acetylcholinesterases are involved in an enzymatic process.Cholinesterase Inhibitors: Drugs that inhibit cholinesterases. The neurotransmitter ACETYLCHOLINE is rapidly hydrolyzed, and thereby inactivated, by cholinesterases. When cholinesterases are inhibited, the action of endogenously released acetylcholine at cholinergic synapses is potentiated. Cholinesterase inhibitors are widely used clinically for their potentiation of cholinergic inputs to the gastrointestinal tract and urinary bladder, the eye, and skeletal muscles; they are also used for their effects on the heart and the central nervous system.Thiocholine: A mercaptocholine used as a reagent for the determination of CHOLINESTERASES. It also serves as a highly selective nerve stain.Butyrylcholinesterase: An aspect of cholinesterase (EC The process of cleaving a chemical compound by the addition of a molecule of water.Kinetics: The rate dynamics in chemical or physical systems.Substrate Specificity: A characteristic feature of enzyme activity in relation to the kind of substrate on which the enzyme or catalytic molecule reacts.