Succinate dehydrogenase (SDH) is an enzyme that catalyzes the oxidation of succinate to fumarate in the Krebs cycle and a critical integral component of the electron transport chain. During ischemia, succinate accumulates and its oxidation by SDH drives reactive oxygen species production that underlies ischemia/reperfusion injury (I/R). Therefore, the inhibition of this enzyme represents a therapeutic potential for the treatment and prevention of damage due to reperfusion due to ischemia. Malonate-derived ester prodrugs, such as dimethyl malonate (DMM) and diethyl malonate (DEM), have been described as cell-permeable substances capable of inhibiting SDH. Despite the fact that these compounds have been used in various studies for the above purpose, no tests have been carried out to prove such an inhibitory effect at the mitochondrial level. Therefore, in this study, a comparison was made of DMM and DEM effect on the enzyme of isolated mitochondria; based on oxygen consumption and spectrophotometric measurement of the enzymatic activity, using the malonate as inhibitor 10 mM (control). The results obtained based on the measurement of the oxygen consumption of the succinate oxidase (Complexes II-IV) showed that the two substances studied did not act inhibitory at concentrations equal to those of malonate. In addition, the assays based on the reduction of Dichlorophenolindolephenol (DCIP) in a time course and the non-linear least squares adjustment, allowed to obtain kinetic parameters for traces without drug (C), with DMM and DEM shown in Table 1. In turn, using molecular docking, it was possible to know the binding mechanisms of these molecules to the enzyme and relate this to their effects. Another important factor is the size of the acyl group linked by the ester bond of the two prodrugs, which is relatively small, so the esterases were unable of hydrolyzing these molecules so that they cannot bind to the malonate site of action into SDH. In conclusion, both DMM and DEM do not act as inhibitors while as non-essential activators of SDH. Therefore, the role they play in the treatment and prevention of ischemia/reperfusion must be reformulated.

Evaluation on inhibition effect of malonate prodrugs in bovine liver isolated mitochondrial succinate dehydrogenase

ACS Fall 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.