Cholinergic system butyrylcholinesterase

The body contains two main classes of cholinesterase acetylcholinesterase (EC 3.1.1.7) and butyrylcholinesterase (EC 3.1.1.8).27 The former, sometimes referred to as true cholinesterase, Is mainly a tissue enzyme and Is found mainly In such tissues as the synapses of the cholinergic system It Is also found In other tissues, such as erythrocytes, where Its function Is uncertain. The latter, referred to as pseudocholinesterase, Is a soluble enzyme that is synthesized In the liver and circulates in the plasma-... 

There are two t)y)es of ChEs, acetylcholinesterase (AChE EC 3.1.1.7) and butyrylcholinesterase (BChE EC.3.1.1.8). AChE plays a major role in the cholinergic system terminating the action of the neurotransmitter acetylcholine (ACh). Inhibition of AChE leads to accumulation of ACh in synapses and blockade of cholinergic... 

The cholinesterases, acetylcholinesterase and butyrylcholinesterase, are serine hydrolase enzymes. The biological role of acetylcholinesterase (AChE, EC 3.1.1.7) is to hydrolyze the neurotransmitter acetylcholine (ACh) to acetate and choline (Scheme 6.1). This plays a role in impulse termination of transmissions at cholinergic synapses within the nervous system (Fig. 6.7) [12,13]. Butyrylcholinesterase (BChE, EC 3.1.1.8), on the other hand, has yet not been ascribed a function. It tolerates a large variety of esters and is more active with butyryl and propio-nyl choline than with acetyl choline [14]. Structure-activity relationship studies have shown that different steric restrictions in the acyl pockets of AChE and BChE cause the difference in their specificity with respect to the acyl moiety of the substrate [15]. AChE hydrolyzes ACh at a very high rate. The maximal rate for hydrolysis of ACh and its thio analog acetyl-thiocholine are around 10 M s , approaching the diffusion-controlled limit [16]. 

Chole- Relating to the biliary system, cholestasis The failure of the normal bile flow to the intestine, causing cholestatic jaundice, cholinergic Nerve fibres that release ACETYLCHOLINE, cholinesterases Enzymes that hydrolyse choline esters, especially ACETYLCHOLINE of which there are two main forms acetylcholinesterase ( true cholinesterase ) is specific for acetylcholine, rapid in this action, and has a discrete distribution being especially located near cholinergic nerve terminals (and in erythrocytes) butyrylcholinesterase ( pseudo cholinesterase) is less selective and is able to hydrolyse some drugs (e.g. SUCCINYLCHOLINE CHLORIDE). Many drugs are known that inhibit the action of these enzymes. See anticholinesterases. chromatin A protein found in the nucleus which stains with basic dyes. It is used in the study of the behaviour of... 

Tacrine (initially 10 mg p.o. q.i.d.) is indicated in the treatment of mild to moderate dementia of the Alzheimer s type. Although many neuronal systems are affected in Alzheimer s disease, the decline in central cholinergic activity is one of the most pronounced neurotransmitter deficits. Tacrine s primary effect is the reversible inhibition of cholinesterase—butyrylcholinesterase more than acetylcholinesterase. This inhibition increases the level of acetylcholine in the central nervous system. In fact, increased levels of acetylcholine have been detected in the cerebrospinal fluid of patients receiving tacrine (see also Figure 12). 

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