An important type of
enzyme that performs
redox reactions in the cell using
NAD or
NADH as a
cofactor. Most neccesarily contain a
rossman fold to bind the dinucleotide as one domain, with the
substrate binding region as another domain. Essentially, this is
modular design of a protein with the two functions (cofactor binding and substrate binding) as separate evolutionary units. Since DHs are essential to most
metabolic pathways, including
glycolysis and the
TCA cycle, it is possible that they are quite ancient proteins.