Electroneutral antiporter that most probably mediates the transport of adenyl nucleotides through the inner mitochondrial membrane (By similarity). Has calcium-dependent ATP-magnesium/inorganic phosphate antiporter activity (PubMed:30080851, PubMed:34346195). Could also have a broader specificity for adenyl nucleotides (By similarity). By regulating the mitochondrial matrix adenyl nucleotide pool, could adapt to changing cellular energetic demands and indirectly regulate adenyl nucleotide-dependent metabolic pathways (By similarity). Acts downstream of Ca(2+)-permeable cation channel PKD2/TRPP2 and it is likely that PKD2-mediated Ca(2+) signaling activates SLC25A25 antiporter activity (By similarity). Required for left-right pattern specification (By similarity). {ECO:0000250|UniProtKB:A2CEQ0, ECO:0000250|UniProtKB:Q6NUK1, ECO:0000269|PubMed:30080851, ECO:0000269|PubMed:34346195}. This is the function of SLC25A25 (solute carrier family 25 member 25, Ensembl gene identifier ENSG00000148339).