The function of Ensembl gene identifier ENSG00000103202 (NME4, NME/NM23 nucleoside diphosphate kinase 4) is as follows. Mitochondria-specific nucleoside diphosphate kinase that catalyzes the transfer of a gamma-phosphoryl group from ATP to a nucleoside diphosphate via a ping-pong mechanism involving a phosphohistidine intermediate, participating in nucleoside triphosphate homeostasis (PubMed:10799505, PubMed:16313181, PubMed:18635542, PubMed:23150663). In vitro, purine nucleoside triphosphates are much more effective as donors and acceptors than pyrimidine nucleoside triphosphates, and ribonucleosides derivatives are superior to their deoxyribonucleosides counterparts (By similarity). Associates with cardiolipin-containing mitochondrial inner membrane and locally produces ADP in the mitochondrial intermembrane space, which is directly taken up via the ADP/ATP translocase (ANT) into the matrix to stimulate respiratory ATP regeneration (PubMed:18635542, PubMed:24970086). Also directly provides GTP for mitochondrial GTPases, such as the dynamin-related GTPase OPA1 (PubMed:24970086). Additionally, catalyzes the anionic phospholipid transfer, namely cardiolipin, from the mitochondrial inner membrane (IM) to the outer membrane (OM) through the formation of contact sites between IM and OM, in a nucleoside diphosphate kinase-independent manner (PubMed:17028143, PubMed:23150663). The switch between the nucleoside diphosphate kinase and the phospholipid transfer activity may depend on the availability and accessibility of cardiolipin and other anionic phospholipids in the IM outer leaflet and OM inner leaflet (PubMed:23150663). {ECO:0000250|UniProtKB:P87355, ECO:0000269|PubMed:10799505, ECO:0000269|PubMed:16313181, ECO:0000269|PubMed:17028143, ECO:0000269|PubMed:18635542, ECO:0000269|PubMed:23150663, ECO:0000269|PubMed:24970086, ECO:0000305, ECO:0000305|PubMed:24970086}.