Biochemical characterization and identification of ferulenol and embelin as potent inhibitors of malate:quinone oxidoreductase from Campylobacter jejuni

Campylobacter jejuni infection poses a serious global threat to public health. The increasing incidence and antibiotic resistance of this bacterial infection have necessitated the adoption of various strategies to curb this trend, primarily through developing new drugs with new mechanisms of action. The enzyme malate:quinone oxidoreductase (MQO) has been shown to be essential for the survival of several bacteria and parasites. MQO is a peripheral membrane protein that catalyses the oxidation of malate to oxaloacetate, a crucial step in the tricarboxylic acid cycle. In addition, MQO is involved in the reduction of the quinone pool in the electron transport chain and thus contributes to cellular bioenergetics. The enzyme is an attractive drug target as it is not conserved in mammals. As a preliminary step in assessing the potential application of MQO from C. jejuni (CjMQO) as a new drug target, we purified active recombinant CjMQO and conducted, for the first time, biochemical analyses of MQO from a pathogenic bacterium. Our study showed that ferulenol, a submicromolar mitochondrial MQO inhibitor, and embelin are nanomolar inhibitors of CjMQO. We showed that both inhibitors are mixed-type inhibitors versus malate and noncompetitive versus quinone, suggesting the existence of a third binding site to accommodate these inhibitors; indeed, such a trait appears to be conserved between mitochondrial and bacterial MQOs. Interestingly, ferulenol and embelin also inhibit the in vitro growth of C. jejuni, supporting the hypothesis that MQO is essential for C. jejuni survival and is therefore an important drug target

Biochemical characterization and identification of ferulenol and embelin as potent inhibitors of malate:quinone oxidoreductase from Campylobacter jejuni

Campylobacter jejuni infection poses a serious global threat to public health. The increasing incidence and antibiotic resistance of this bacterial infection have necessitated the adoption of various strategies to curb this trend, primarily through developing new drugs with new mechanisms of action. The enzyme malate:quinone oxidoreductase (MQO) has been shown to be essential for the survival of several bacteria and parasites. MQO is a peripheral membrane protein that catalyses the oxidation of malate to oxaloacetate, a crucial step in the tricarboxylic acid cycle. In addition, MQO is involved in the reduction of the quinone pool in the electron transport chain and thus contributes to cellular bioenergetics. The enzyme is an attractive drug target as it is not conserved in mammals. As a preliminary step in assessing the potential application of MQO from C. jejuni (CjMQO) as a new drug target, we purified active recombinant CjMQO and conducted, for the first time, biochemical analyses of MQO from a pathogenic bacterium. Our study showed that ferulenol, a submicromolar mitochondrial MQO inhibitor, and embelin are nanomolar inhibitors of CjMQO. We showed that both inhibitors are mixed-type inhibitors versus malate and noncompetitive versus quinone, suggesting the existence of a third binding site to accommodate these inhibitors; indeed, such a trait appears to be conserved between mitochondrial and bacterial MQOs. Interestingly, ferulenol and embelin also inhibit the in vitro growth of C. jejuni, supporting the hypothesis that MQO is essential for C. jejuni survival and is therefore an important drug target

Biochemical characterization and identification of ferulenol and embelin as potent inhibitors of malate:quinone oxidoreductase from Campylobacter jejuni

Campylobacter jejuni infection poses a serious global threat to public health. The increasing incidence and antibiotic resistance of this bacterial infection have necessitated the adoption of various strategies to curb this trend, primarily through developing new drugs with new mechanisms of action. The enzyme malate:quinone oxidoreductase (MQO) has been shown to be essential for the survival of several bacteria and parasites. MQO is a peripheral membrane protein that catalyses the oxidation of malate to oxaloacetate, a crucial step in the tricarboxylic acid cycle. In addition, MQO is involved in the reduction of the quinone pool in the electron transport chain and thus contributes to cellular bioenergetics. The enzyme is an attractive drug target as it is not conserved in mammals. As a preliminary step in assessing the potential application of MQO from C. jejuni (CjMQO) as a new drug target, we purified active recombinant CjMQO and conducted, for the first time, biochemical analyses of MQO from a pathogenic bacterium. Our study showed that ferulenol, a submicromolar mitochondrial MQO inhibitor, and embelin are nanomolar inhibitors of CjMQO. We showed that both inhibitors are mixed-type inhibitors versus malate and noncompetitive versus quinone, suggesting the existence of a third binding site to accommodate these inhibitors; indeed, such a trait appears to be conserved between mitochondrial and bacterial MQOs. Interestingly, ferulenol and embelin also inhibit the in vitro growth of C. jejuni, supporting the hypothesis that MQO is essential for C. jejuni survival and is therefore an important drug target

Biochemical Studies of Mitochondrial Malate: Quinone Oxidoreductase from Toxoplasma gondii

Toxoplasma gondii is a protozoan parasite that causes toxoplasmosis and infects almost one-third of the global human population. A lack of effective drugs and vaccines and the emergence of drug resistant parasites highlight the need for the development of new drugs. The mitochondrial electron transport chain (ETC) is an essential pathway for energy metabolism and the survival of T. gondii. In apicomplexan parasites, malate:quinone oxidoreductase (MQO) is a monotopic membrane protein belonging to the ETC and a key member of the tricarboxylic acid cycle, and has recently been suggested to play a role in the fumarate cycle, which is required for the cytosolic purine salvage pathway. In T. gondii, a putative MQO (TgMQO) is expressed in tachyzoite and bradyzoite stages and is considered to be a potential drug target since its orthologue is not conserved in mammalian hosts. As a first step towards the evaluation of TgMQO as a drug target candidate, in this study, we developed a new expression system for TgMQO in FN102(DE3)TAO, a strain deficient in respiratory cytochromes and dependent on an alternative oxidase. This system allowed, for the first time, the expression and purification of a mitochondrial MQO family enzyme, which was used for steady-state kinetics and substrate specificity analyses. Ferulenol, the only known MQO inhibitor, also inhibited TgMQO at IC50 of 0.822 μM, and displayed different inhibition kinetics compared to Plasmodium falciparum MQO. Furthermore, our analysis indicated the presence of a third binding site for ferulenol that is distinct from the ubiquinone and malate sites