alanine racemase activity

Definition

Target type: molecularfunction

Catalysis of the reaction: L-alanine = D-alanine. [EC:5.1.1.1, RHEA:20249]

Alanine racemase activity is a crucial enzymatic process that interconverts the L- and D-enantiomers of alanine, a non-essential amino acid. This interconversion is critical for various biological functions, including bacterial cell wall synthesis, neurotransmitter production, and the biosynthesis of specific secondary metabolites.

The active site of alanine racemase typically harbors a pyridoxal 5'-phosphate (PLP) cofactor, which acts as a catalytic coenzyme. The mechanism involves several steps:

1. **Substrate Binding:** L-alanine binds to the active site, forming a Schiff base with the PLP cofactor.
2. **α-Proton Abstraction:** A base within the active site abstracts the α-proton from the bound L-alanine, generating a carbanionic intermediate.
3. **Configuration Inversion:** The carbanionic intermediate undergoes a conformational change, flipping the configuration of the α-carbon.
4. **Protonation:** A proton from the solvent or another amino acid residue is transferred to the carbanionic intermediate, regenerating the C-H bond.
5. **Product Release:** The newly formed D-alanine is released from the active site, allowing the enzyme to bind another substrate molecule.

The racemization process catalyzed by alanine racemase is essential for bacterial cell wall synthesis, as D-alanine is a key component of peptidoglycans. In some bacteria, alanine racemase is a target for antimicrobial drugs, as its inhibition can disrupt cell wall formation and lead to bacterial death.

In addition to its role in bacterial cell wall synthesis, alanine racemase activity is also implicated in neurotransmitter production, specifically the synthesis of D-serine, which serves as a co-agonist at the NMDA receptor in the brain.

Furthermore, alanine racemase activity is involved in the biosynthesis of specific secondary metabolites, such as the antibiotic bacitracin, which inhibits bacterial cell wall synthesis by blocking the dephosphorylation of lipid intermediates.

In conclusion, alanine racemase activity plays a fundamental role in various biological processes, from bacterial cell wall synthesis to neurotransmitter production and secondary metabolite biosynthesis. The enzyme's ability to interconvert L- and D-alanine enantiomers makes it a crucial player in cellular metabolism and a potential target for drug development.'
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Proteins (2)

Compounds (2)