The substrate specificity of l-alanine dehydrogenase

l-Alanine dehydrogenase complexes with l-alanine and several of its analogues. Glycine, sarcosine and structural analogues of alanine having alkyl, hydroxymethyl or thiomethyl substitutions on the α-carbon of alanine bind with the enzyme. The l-isomers of these amino acids are substrates while the d-isomers, glycine, and sarcosine are competitive inhibitors of l-alanine deamination. Substitution or modification of the -COOH group, the -NH 2 group or the -H of the α-carbon of l-alanine results in complete loss of complexing ability. As in the case of glutamic acid dehydrogenase, l-alanine dehydrogenase metabolizes aliphatic amino acids with chain lengths of less than 7 carbons and is inhibited by the d-isomers of its substrates.