This enzyme belongs to the family of isomerases, specifically those racemases and epimerases acting on amino acids and derivatives.

The enzyme is absent in higher eukaryotes but found everywhere in prokaryotes, making alanine racemase a great target for antimicrobial drug development.

However, knockout studies have shown that without the alr gene being expressed, the bacteria would need an external source of D-alanine in order to survive.

[4] Structural studies of enzyme complexes with a synthetic L-alanine analog, a tight binding inhibitor [5] and propionate [6] further validate that Tyr265 and Lys39 are catalytic bases for the reaction,.

An interaction between both the phosphate oxygen and pyridine nitrogen atoms to the 5’phosphopyridoxyl region of PLP-Ala probably creates tight binding to the enzyme.

The N-terminal domain is also found in the PROSC (proline synthetase co-transcribed bacterial homolog) family of proteins, which are not known to have alanine racemase activity.

The second catalytic residue is pre-positioned to donate a proton quickly after a carbanionic intermediate is formed and thus reduces the chance of alternative reactions occurring.

There are two potential conflicts with this traditional mechanism, as identified by Watanabe et al. First, Arg219 forms a hydrogen bond with pyridine nitrogen of PLP.

Another problem identified was the need for another basic residue to return Lys39 and Tyr265 back to their protonated and unprotonated forms for L-alanine and vice versa for D-alanine.

Watanabe et al. found no amino acid residues or water molecules, other than the carboxylate group of PLP-Ala, to be close enough (within 4.5A) to protonate or deprotonate Lys or Tyr.