Activity O Cholinesterase and Its Inhibitors
Enzymes are highly specific biological catalysts (proteins) that influence the rate of metabolic reactions (Smith, 1997). They are responsible for efficiently converting substrate molecules into products required to sustain life (Grisham et al., 1999). The activity of enzymes can often be effected by other endogenous or foreign factors (e.g. inhibitors). Inhibitors are able to decrease the rate of enzymatic activity by binding to the enzyme and preventing it from functioning optimally (Hostettmann et al., 2006). Inhibitors occur both naturally (i.e. plant and animal poisons) and as artificially synthesized substances (i.e. insecticides such as malathion) (Walsh et al., 2011). They are also common in pharmocology and biochemistry, as many drugs are essentially enzyme inhibiting molecules used clinically to help treat conditions such as glaucoma, myasthenia gravis and Alzheimer 's disease (Scapin, 2006; Liston et al., 2004).
In this particular experiment, we are attempting to calculate the rate of the reaction (hydrolysis) of different substrates by enzymes acetylcholinesterase and butyrylcholinesterase, in the presence of various inhibitors (anticholinesterases). Acetylcholinesterase (or erythrocyte cholinesterase) is mainly found in red blood cells, neural synapse, cholinergic nerve fibres and muscle motor end-plates (Wang & Tang, 2005). Butyrylcholinesterase (or pseudocholinesterase) is localized in the plasma and liver, and unlike AChE prefers to hydrolise butyrylcholine, benzoylchline, procaine and suxamethonium more so than acetylcholine (Brash, 2009).
For the purposes of this experiment, activity of the enzymes will be measured based on visual observation of the change in colour of phenol red in a dilute buffer containing sodium diethylbarbiturate. The characteristic liberation of acid can be linked to this change in colour (decrease in basic from of the buffer) and
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