UDP-N-Acetylglucosamine enolpyruvyl transferase (MurA) of Acinetobacter baumannii (AbMurA): Structural and functional properties

- Recombinant AbMurA exists as a monomer in solution.
- The Km for substrates- UDP-N-acetylglucosamine and PEP were determined.
- Enzymatic activity was inhibited ∼3 fold in presence of 50 mM fosfomycin.
- The conserved FFQ-binding site included the surface loop containing the active site Cys116.

Peptidoglycan (PG) is the key component of the bacterial cell wall. The enzyme UDP-N-Acetylglucosamine Enolpyruvyl Transferase (MurA) catalyzes the transfer of enolpyruvate from phosphoenolpyruvate (PEP) to uridinediphospho-N-acetylglucosamine (UNAG), which is the first committed step of PG biosynthesis. Here, we present the biochemical and structural features of the MurA enzyme of the opportunistic pathogen Acinetobacter baumannii (AbMurA). The recombinant AbMurA exists as a monomer in solution and shows optimal activity at pH 7.5 and 37 °C. The Km for UDP-N-acetylglucosamine was 1.062 ± 0.09 mM and for PEP was 1.806 ± 0.23 mM. The relative enzymatic activity was inhibited ∼3 fold in the presence of 50 mM fosfomycin (FFQ). Superimposition of the AbMurA model with E. coli demonstrated key structural similarity in the FFQ-binding site. AbMurA also has a surface loop that contains the active site Cys116 that interact with FFQ. Sequence analysis indicates the presence of the five conserved amino acids, i.e., K22, C116, D306, D370 and L371, required for the functional activity like other MurA enzymes from different bacteria. MurA enzymes are indispensable for cell integrity and their lack of counterparts in eukaryotes suggests them to be a promising drug target.