Glutamate, leucine, phenylalanine and valine dehydrogenases are structurally and functionally related. They contain a Gly-rich region containing a conserved Lys residue, which has been implicated in the catalytic activity, in each case a reversible oxidative deamination reaction.

Glutamate dehydrogenases (EC: 1.4.1.2, EC: 1.4.1.3, and EC: 1.4.1.4) (GluDH) are enzymes that catalyze the NAD- and/or NADP-dependent reversible deamination of L-glutamate into alpha-ketoglutarate [PMID:1358610, PMID:8315654]. GluDH isozymes are generally involved with either ammonia assimilation or glutamate catabolism. Two separate enzymes are present in yeasts: the NADP-dependent enzyme, which catalyses the amination of alpha-ketoglutarate to L-glutamate; and the NAD-dependent enzyme, which catalyses the reverse reaction [PMID:2989290] - this form links the L-amino acids with the Krebs cycle, which provides a major pathway for metabolic interconversion of alpha-amino acids and alpha- keto acids [PMID:3368458].

Leucine dehydrogenase (EC: 1.4.1.9) (LeuDH) is a NAD-dependent enzyme that catalyzes the reversible deamination of leucine and several other aliphatic amino acids to their keto analogues [PMID:3069133]. Each subunit of this octameric enzyme from Bacillus sphaericus contains 364 amino acids and folds into two domains, separated by a deep cleft. 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.