Structural insights into the alanine racemase from Enterococcus faecalis.

Area of Science:

• Biochemistry
• Structural Biology
• Microbiology

Background:

• Alanine racemase (AlaR) is a crucial bacterial enzyme for peptidoglycan synthesis.
• AlaR is absent in eukaryotes, making it a promising antibacterial drug target.
• Pyridoxal 5'-phosphate (PLP)-dependent enzymes include AlaR, belonging to the fold-type III group.

Purpose of the Study:

• To determine the crystal structures of Enterococcus faecalis v583 alanine racemase (apoenzyme and d-cycloserine complex).
• To provide structural insights for the development of new antibiotics targeting bacterial AlaR.

Main Methods:

• X-ray crystallography was used to obtain the crystal structures.
• The structures were determined at a resolution of 2.5 Å.
• Analysis of hydrogen bonding interactions between DCS and active site residues.

Main Results:

• The crystal structures of both apo-AlaR and the AlaR-d-cycloserine (DCS) complex were elucidated.
• DCS, a suicide inhibitor, forms hydrogen bonds with conserved active site residues Tyr44 and Ser207.
• The apoenzyme structure revealed three monomers with a polyethylene glycol molecule at the dimer interface.

Conclusions:

• Structural data provides key insights into AlaR function and inhibition.
• These findings can guide the rational design of novel antibiotics targeting bacterial alanine racemase.
• The study highlights AlaR as a viable target for combating pathogenic bacteria.