Study of relationship of physiological roles and pathogenicity of aggressive periodontopathic bacterial quinol peroxidase

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Quinol peroxidase (QPO) of Aggregatibacter actinomycetemcomitans catalyzes peroxidase activity using a quinol on respiratory chain.Aqpo null mutant exhibits an oxidative stress phenotype, suggesting that QPO plays animportant role in scavenging endogenously generated hydrogen peroxide, and exhibitsreduced production of leukocyte (LtxA), a secreted bacterial toxin that is known to targethuman leukocytes. Screening identified ascofuranone as a highly potent inhibitor of QPO(Ki = 9.6 nM). This inhibitor also reduced the secretion of LtxA, with an associatedreduction in the pathogenicity ofA. actinomycetemcomitans for HL-60 cells. We producedthe recombinant QPO expression system inEscherichia coli. Purified recombinant QPOwas used to analyse the catalytic mechanism, indicating that QPO catalyzes as ping pongbi bi mechanism.