Recombinant broad-range phospholipase C from Listeria monocytogenes exhibits optimal activity at acidic pH

• Zn2+-dependence, substrate preferences, and active site residues of PLC from Listeria monocytogenes were characterized.
• The distinct acidic pH optimum for LmPLC activity suits its role as a virulence factor of the intracellular pathogen.
• The interdependence of LmPLC with another major Listeria virulence factor LLO was evaluated in vitro.

The broad-range phospholipase C (PLC) from Listeria monocytogenes has been expressed using an intein expression system and characterized. This zinc metalloenzyme, similar to the homologous enzyme from Bacillus cereus, targets a wide range of lipid substrates. With monomeric substrates, the length of the hydrophobic acyl chain has significant impact on enzyme efficiency by affecting substrate affinity (Km). Based on a homology model of the enzyme to the B. cereus protein, several active site residue mutations were generated. While this PLC shares many of the mechanistic characteristics of the B. cereus PLC, a major difference is that the L. monocytogenes enzyme displays an acidic pH optimum regardless of substrate status (monomer, micelle, or vesicle). This unusual behavior might be advantageous for its role in the pathogenicity of L. monocytogenes.

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