a) Draw arrows showing the electron movement in this reaction, and include the electron movement in the nicotinamide ring of the NADH coenzyme. This allows a key isomerization step to occur on the sub...a) Draw arrows showing the electron movement in this reaction, and include the electron movement in the nicotinamide ring of the NADH coenzyme. This allows a key isomerization step to occur on the substrate through a protonation-deprotonation mechanism, followed by addition of water, cleavage of the substrate-NAD adduct to regenerate NAD + , and finally tautomerization to the product.