Catalyzes the electroneutral exchange or flux of physiologically important metabolites such as dicarboxylates (malonate, malate, succinate), inorganic sulfur-containing anions, and phosphate, across mitochondrial inner membrane (PubMed:33746082). Plays an important role in gluconeogenesis, fatty acid metabolism, urea synthesis, and sulfur metabolism, particularly in liver, by supplying the substrates for the different metabolic processes (PubMed:33746082, PubMed:16027120, PubMed:30943427). Regulates fatty acid release from adipocytes, and contributes to systemic insulin sensitivity (PubMed:33746082). (S)-malate(in) + phosphate(out) = (S)-malate(out) + phosphate(in) (S)-malate(in) + malonate(out) = (S)-malate(out) + malonate(in) (S)-malate(in) + succinate(out) = (S)-malate(out) + succinate(in) (S)-malate(in) + sulfate(out) = (S)-malate(out) + sulfate(in) malonate(out) + phosphate(in) = malonate(in) + phosphate(out) phosphate(in) + succinate(out) = phosphate(out) + succinate(in) phosphate(in) + sulfate(out) = phosphate(out) + sulfate(in) malonate(out) + succinate(in) = malonate(in) + succinate(out) Regulated by circadian protein CLOCK (Circadian Locomotor Output Cycles Kaput). Expressed at very high levels in white adipose tissue (PubMed:10567211, PubMed:33746082). And at low levels in brown adipose tissue, kidney and liver (PubMed:10567211). Belongs to the mitochondrial carrier (TC 2.A.29) family.