 The nicotinamide ring of the NAD+ cofactor binds deep in this cleft, which is thought to close during the hydride transfer step of the catalytic cycle.Phenylalanine dehydrogenase (PheDH) is an NAD-dependent enzyme that catalyses the reversible deamidation of L-phenylalanine into phenyl-pyruvate.Valine dehydrogenase (ValDH) is an NADP-dependent enzyme that catalyses the reversible deamidation of L-valine into 3-methyl-2-oxobutanoate.