AChE_lab_report - Introduction The ability to monitor...

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Introduction The ability to monitor enzyme activity is an essential tool for many types of studies. Acetylcholine (ACh) is a biological molecule that functions as a neurotransmitter in many living organisms. Human muscles are innovated by neurons known as motoneurons (or motor neurons) which release ACh into the sole junction formed between motoneuron and muscle fiber. (Durfee, 2008) ACh is an ester which is broken down by the substrate specific esterase; acetylcholinesterase (AChE). This official name minimizes ambiguity because it is named by the substrate to which it is specific; followed by a word ending in – ase which specifies the type of reaction which it catalyzes. (Voet et al. 2008) Acetylcholin esterase is an esterase. An esterase catalyzes a chemical reaction such that the ester substrate is chemically hydrolyzed into an acid and an alcohol; acetylcholine into the products acetic acid and choline. (O’Neal et al. 2010) Biological catalysts, such as AChE, are essential for biological processes. They often serve in a regulatory capacity. The concentration of the enzyme can reflect the needs of the synapse such that the appropriate concentration of the substrate is available to the post synaptic receptors. Tampering with the concentration of AChE can have hazardous effects on the biological systems of an organism. As such, it can be found in pesticides with the intent to harm the biological processes of insects via increasing the concentration of this enzyme. Manipulations of AChE’s effective concentrations also have had medicinal value for humans. The reversible inhibition of AChE activity has been used in the treatment of CNS disorders such as Alzheimer’s and Parkinson’s disease. The decreased enzyme activity alleviates some symptoms associated with these diseases via increased substrate concentrations. (Srikumar et al. 2004) Auletta, Chriss –ID- 106 841 628 –Lab- 204 L-05 Page 1
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The Ellman method is utilized to assay AChE activity via the replacement of the biological substrate common to many organisms (ACh) with the commercial product acetylthiocholine (ATC). (O’Neal et al. 2010) The products of the artificial substrate are acetic acid and thiocholine. Thiocholine contains a sulfhydryl group (-SH) which reacts with 5,5’-dithio-bis-(2-nitrobenzoic acid) (DTNB 2- ) ; a clear molecule known as Ellman’s reagent. (O’Neal et al. 2010) Ellman’s reagent reacts with the sulfhydryl functional group at a 1:1 ratio such that the thiocholine released reacts with Ellman’s reagent (DTNB 2- ) and is thus reduced to thionitrobenzoic acid and a mixed disulfide molecule. The mixed disulfide molecule contains one of the initial reaction products; thiocholine.
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AChE_lab_report - Introduction The ability to monitor...

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