Mitochondrial malate dehydrogenase that catalyzes the reversible conversion of malate to oxaloacetate using NAD(+) as a cofactor (PubMed:27989324). Plays a central role in the tricarboxylic acid (TCA) cycle contributing to cellular respiration and energy production via the mitochondrial electron transport chain (PubMed:35366151). Also participates in the malate-aspartate NADH shuttle, facilitating transfer of reducing equivalents between cytosol and mitochondria to maintain redox balance (NAD(+)/NADH homeostasis) and support metabolic flux between compartments (By similarity). In addition to its metabolic role, binds to RNA in cells, associating with cytosolic RNAs including tRNAs and mRNAs (PubMed:38609156). {ECO:0000250|UniProtKB:P08249, ECO:0000269|PubMed:27989324, ECO:0000269|PubMed:35366151, ECO:0000269|PubMed:38609156, ECO:0000269|PubMed:39738099}. This is the function of MDH2 (malate dehydrogenase 2, Ensembl gene identifier ENSG00000146701).