fumarates and 2-phenylsuccinate

In this study, we investigated the metabolite permeability of isolated coupled Saccharomyces cerevisiae mitochondria. The occurrence of a fumarate/malate antiporter activity was shown. The activity differs from that of the dicarboxylate carrier (which catalyses the succinate/malate antiport) in (a) kinetics (Km and Vmax values are about 27 microM and 22 nmol min(-1) mg protein(-1) and 70 microM and 4 nmol min(-1) mg protein(-1), respectively), (b) sensitivity to inhibitors, (c) Ki for the competitive inhibitor phenylsuccinate and (d) pH profiles.

Topics: Adenosine Diphosphate; Adenosine Triphosphate; Antiporters; Biological Transport, Active; Fumarates; Hydrogen-Ion Concentration; Kinetics; Malates; Mitochondria; Saccharomyces cerevisiae; Succinates

Fumarate permeation in isolated rat liver mitochondria was demonstrated by measuring malate and phosphate efflux caused by fumarate added externally to the mitochondrial suspension. The existence of two specific fumarate translocators, fumarate/malate and fumarate/phosphate, is shown here. These carriers are distinguished in the light of different kinetic parameters (Km values are 50 microM and 150 microM, and Vmax values are 17 and 40 nmoles/min X mg mitochondrial protein, respectively) and of differing sensitivity to non-penetrant compounds. Fumarate was found to cause oxaloacetate efflux from mitochondria by means of an indirect process which involves the cooperation of both fumarate/malate and malate/oxaloacetate translocators. Results are discussed in the light of the physiological role played by fumarate translocation in both ureogenesis and aminoacid metabolism.

Topics: Animals; Biological Transport, Active; Citric Acid Cycle; Ethylmaleimide; Fumarates; Kinetics; Malates; Malonates; Mersalyl; Mitochondria, Liver; Models, Biological; Phosphates; Rats; Succinates