D-amino acids are essential components of the bacterial cell wall and play notable roles in microbiology
as regulators, for example in sporulation, biofilm formation or interspecies communication. Racemases are the specific
enzymes catalyzing the interconversion of L-amino acids to D-amino acids. While most of racemases are
mono-specific, a family of broad-spectrum racemases that can racemize ten of the 19 natural chiral amino acids has
been recently reported. These enzymes can interconvert radically different residues such as aliphatic and positively
charged residues producing non-canonical D-amino acids. Crystal structures together with bioinformatics allowed identification of the
residues defining the molecular footprint in broad-spectrum racemases, the specific features of their active sites and the structural basis of
their promiscuity. Here we review the recent knowledge on this family compared with the well established of alanine racemases. This
structural information is a prerequisite for the development of novel drugs against the important human pathogens for which broadspectrum
racemases play a key role.
Keywords: Non-canonical D-amino acids, racemases, bioinformatics; antibiotics resistance, X-ray crystallography.
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