The area where substrates and co-factors bind to the enzyme is called the active site. This is where the catalysis takes place. An active site often appears like a pocket, and consists of several amino acids which can have specific interactions with the substrate [1]. Figure 1 shows the active site of alcohol dehydrogenase where NAD+ binds. Amino acid residue 47, which is responsible for the Alcohol Flush syndrome is located in this active site, and this amino acid is important in binding to NAD+. If a mutation causes an amino acid substitution on this residue, the kinetic parameters may therefore be altered, which is the case in the Alcohol Flush syndrome.

On a model of alcohol dehydrogenase the active site where NAD+ can bind to, is colored blue and NAD+ is colored red

Figure 1: Surface model of alcohol dehydrogenase showing the active site (blue) for NAD+ (red) binding. Generated with PyMOL from PDB entry 1HSZ


  1. Lehninger, Albert L.; Nelson, David L.; Cox, Michael M. (2008). Principles of Biochemistry (5th ed.). New York, NY: W.H. Freeman and Company. ISBN 978-0-7167-7108-1.

ADH Substrate

Theory overview