Public Thesis defense - LIBST

Exploration and Characterization of a Superfamily of Nickel-Dependent Hydroxy Acid Racemases and Epimerases by Julian URDIAIN-ARRAIZA

Pour l’obtention du grade académique de Doctorat en Sciences

Hydroxy acids (HAs) are organic carboxylic acids omnipresent in the living world and serve as essential building blocks for various industries, including food, cosmetics, and pharmaceuticals. Recently, a superfamily of nickel-dependent HA racemases and epimerases using the nickel-pincer nucleotide (NPN) cofactor was discovered: the LarA superfamily. This enzyme superfamily is present in all domains of life and holds potential for use in the stereoselective conversion of chiral HAs. However, the study of the LarA superfamily is still in its infancy, and much remains to be understood about the full range of reactions catalyzed by these enzymes, the LarA homologs (LarAHs).

This thesis delves into the exploration and biotechnological potential of the LarA superfamily through biochemical characterization, taxonomic analysis, and structural modeling. We developed a versatile capillary electrophoresis (CE) method for highly efficient chiral analysis of underivatized α-, β- and poly-hydroxy acids (AHAs, BHAs, PHAs). Using this novel CE method, we explored and expanded five different LarAH families within the LarA superfamily: lactate racemases (LARs), short-chain aliphatic HA racemases (SARs), malate racemases (MARs), hydroxyglutarate racemases (HGRs), and D-gluconate 2-epimerase (GntEs). We also identified two novel families of LarAHs: hydrophobic HA racemases (HHRs), and broad-spectrum HA isomerases (BSHIs). In total, we overexpressed, purified, and characterized 13 LarAHs, revealing 11 novel AHA racemization reactions and 23 novel PHA/sugar acid C2-epimerization reactions.

Altogether, these findings widely expand the substrate scope of NPN-dependent enzymes from the LarA superfamily, offering new possibilities for producing valuable HA stereoisomers and paving the way for future biotechnological applications of LarAHs.

Jury members :

• Prof. Benoît Desguin (UCLouvain) (Supervisor)
• Prof. Bernard Hallet (UCLouvain) (Chairperson)
• Prof. Patrice Soumillion (UCLouvain)
• Prof. Pierre Morsomme (UCLouvain)
• Prof. Tom Desmet (UGent)
• Prof. Filip Meysman (UAntwerpen)

Pay attention : the public defense of Julian URDIAIN ARRAIZA will also take place in the form of a videoconference

Télécharger l'annonce