The structure of NAD:
The active site is nicotiamide.
The hydride added to NAD+ comes exclusively from the ajdehyde substrate and was pro-R stereospecific. Alcohol DHase and Lactate DHase have the some property.
Pyridine nucleotide-linked enzyme are well known to transferhydride
stereospecifically to the pyridine coenzyme. And the catalytic site of
ALDH is a Cys residue. In this case is Cys-302.
The pro-R fasion for example
