SLC25A45: a gatekeeper for methylated amino acid metabolism.

The metabolite substrates of numerous transporters remain largely elusive. Two recent studies by Khan et al. and Dias et al. identify SLC25A45 as a mitochondrial transporter of methylated amino acids that supports de novo carnitine synthesis, providing a valuable strategy for deorphanizing transporters and novel insights into cytoplasm-mitochondria communication and metabolic coordination.