Lactonase

It catalyzes the reaction Many species of α-, β-, and γ-proteobacteria produce acylated homoserine lactones, small hormone-like molecules commonly used as communication signals between bacterial cells in a population to regulate certain gene expression and phenotypic behaviours.

In hydrolysing the lactone bond, lactonase prevents these signaling molecules from binding to their target transcriptional regulators, thus inhibiting quorum sensing.

[13] A dinuclear zinc binding site is conserved in all known lactonases and essential for enzyme activity and protein folding.

[18] In the phytopathogen A. tumefaciens, AiiB lactonase acts as a fine modulator that essentially delays the release of lactone OC8-HSL and the resultant number of tumors produced by the pathogen.

[26] Plants expressing AHL-Lactonase were shown to demonstrate enhanced resistance to infection from the pathogen Erwinia carotovora.

Presumably, OHHL-hydrolysis via lactonase reduced OHHL levels, inhibiting the quorum-sensing systems driving virulence gene expression.