Birrer Sandbox 2: Difference between revisions

Alcohol dehydrogenase (PDB id [[1htb]]), or ADH, is an enzyme that catalyzes the oxidation of primary and secondary alcohols to their corresponding aldehydes and ketones through a mechanism that involves the removal of hydrogen. In the oxidation mechanism, ADH is momentarily associated with nicontinamide adenine dinucleotide (NAD+), which functions as a cosubstrate. In its reaction, alcohol dehydrogenase uses zinc and NAD to facilitate the reaction. The function of zinc is to position the –OH group on the ethanol in a conformation that allows for the oxidation to occur. NAD then acts as a cosubstrate and performs the oxidation. <scene name='Birrer_Sandbox_2/Adh_plus_zn_and_ethanol/1'>1adc</scene> shows a picture of this interaction, with two ethanol molecules attached to the active sites. In the picture Zinc is positioned between Cys46, Cys174, and His67, all polar side chains. Ethanol, then, binds to the zinc which is next to the NAD cosubstrate. <ref>''Alcohol Dehydrogenase''. [[Protein Data Bank]]. 2010. RCSB. 1 March 2010 <http://www.rcsb.org/pdb/static.do?p=education_discussion/molecule_of_the_month/pdb13_3.html> </ref> The reaction is as follows: CH3CH2OH + NAD+ -> CH3COH (acetaldehyde) + NADH + H+ (Note: The reaction is actually reversible although the arrow does not show it) <ref>Voet, et. al. ''Fundamentals of Biochemistry: 3rd Edition''. Hoboken: Wiley & Sons, Inc, 2008.</ref> The alcohol dehydrogenase reaction is a bisubstrate reaction, where ADH catalyzed the transfer of a hydride ion from ethanol to NAD+. In metabolic reactions within the human liver, glyceraldehyde is reduced to glycerol through a mechanism in which NADH is reduced to NAD+, and this whole process is catalyzed by alcohol dehydrogenase.   

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