Alanine racemase

Structure of alanine racemase

Crystal structure of alanine racemase

Alanine racemase is an enzyme that catalyzes the racemization of alanine, converting the L-alanine to D-alanine and vice versa. This enzyme is crucial in the biosynthesis of D-alanine, an essential component of the bacterial cell wall.

Structure

Alanine racemase is a pyridoxal phosphate (PLP)-dependent enzyme. The enzyme typically exists as a homodimer, with each monomer containing a PLP-binding domain. The active site of alanine racemase is characterized by the presence of a lysine residue that forms a Schiff base with the PLP cofactor.

Active site of alanine racemase

Mechanism

The mechanism of alanine racemase involves the formation of a Schiff base between the PLP cofactor and the substrate. The enzyme facilitates the removal of the _-hydrogen from L-alanine, forming a planar carbanion intermediate. This intermediate can then be reprotonated on the opposite face to form D-alanine.

Mechanism of alanine racemase

Biological function

Alanine racemase plays a critical role in the synthesis of D-alanine, which is a key component of the peptidoglycan layer in bacterial cell walls. This makes the enzyme a target for antibiotic development, as inhibiting alanine racemase can disrupt cell wall synthesis and bacterial growth.

Inhibition

Inhibitors of alanine racemase are of interest as potential antibiotics. These inhibitors often mimic the transition state of the racemization reaction or bind to the PLP cofactor, preventing the enzyme from catalyzing the conversion of L-alanine to D-alanine.

Related pages

• Pyridoxal phosphate
• D-alanine
• Peptidoglycan
• Enzyme inhibition

Gallery

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  Overall structure of alanine racemase
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  Distance between key residues in the active site