Title : Screening of natural components as potential inhibitors of the ATP synthase, a potent target to overcome antibacterial resistance
Most bacteria are harmless and valuable germs whereas some constitute major threats on public health. In fact, Escherichia coli has been recently classified by the World Health Organization (WHO) as being one among other bacteria causing serious antimicrobial resistance. Therefore, new antibiotics and biological targets are needed to overcome this antibacterial resistance. ATP synthase is a highly conserved enzyme embedded in the plasma membrane of bacteria. ATP synthase, the chief generator of adenosine triphosphate (ATP), is involved in almost all biological cellular processes and thus plays a vital role in the survival of bacteria. This enzyme is therefore viewed as a potent pharmaceutical target in the treatment of bacterial infections. Hence, in this study, 20 natural components (essential oil constituents) were screened for their potential inhibitory effect on E. coli ATP synthase. The reaction studied is the hydrolysis of ATP into ADP and inorganic phosphate (Pi) catalyzed by this enzyme.
First, E. coli membrane ATP synthase was isolated via cell lysis. A simple spectrophotometric method was optimized to quantify the released phosphate from ATP hydrolysis in order to follow the enzymatic activity. The method was validated by determining the kinetic parameters of this reaction (Km = 144.66 μM and Vmax = 270.27 μM/min), and through the inhibition assays of ATP synthase using three reference inhibitors, thymoquinone (half maximal inhibitory concentration [IC50] = 50.93 μM), resveratrol (maximum inhibition of 40%), and quercetin (IC50 = 29.01 μM). Among the studied essential oil components, α-terpinene was the most potent inhibitor (IC50 = 19.74 μM) followed by β-pinene, isoeugenol, eugenol, and estragole.
This developed method can be expanded to assess the activity and selectivity of different other natural or synthetic inhibitors against ATP synthase or other membrane-bound enzymes involved in several diseases. Moreover, effective bioactive molecules could be a natural and economical treatment against many bacterial infections and can be used as food additives to prevent bacterial growth.