ETFBKMT (also known as METTL20) is a mitochondrial protein-lysine methyltransferase that selectively trimethylates lysine residues 199-203 in the β-subunit of electron transfer flavoprotein (ETFB) 12. This methylation occurs adjacent to the recognition loop of ETFB, a region critical for binding dehydrogenases involved in fatty acid oxidation and one-carbon metabolism 1. ETFBKMT-mediated methylation negatively regulates ETFB function by reducing its ability to accept electrons from acyl-CoA dehydrogenases, thus modulating electron transfer to the respiratory chain 2. Suppression of ETFBKMT-catalyzed ETFβ trimethylation decreases cellular oxygen consumption during fatty acid oxidation in mitochondria 1. Beyond metabolic function, ETFBKMT has emerged as a candidate gene associated with neurodevelopmental disorders; genomic deletions encompassing ETFBKMT have been identified in patients with intellectual disability and Kallmann syndrome, suggesting dosage-sensitive involvement in cognitive and neurological development 34. Additionally, ETFBKMT expression correlates with hepatic fibrosis progression, where it may contribute to reactive oxygen species production and fibrogenic signaling 5.