DLD (dihydrolipoamide dehydrogenase) is a mitochondrial flavin-dependent enzyme that functions as the E3 component of three alpha-ketoacid dehydrogenase complexes: pyruvate dehydrogenase, alpha-ketoglutarate dehydrogenase, and branched-chain amino acid dehydrogenase 12. As part of these complexes, DLD catalyzes reoxidation of the dihydrolipoyl moiety on E2 subunits using NAD+ as the ultimate electron acceptor 2345. This activity links cytoplasmic glycolysis to the mitochondrial tricarboxylic acid cycle. DLD also functions in the glycine cleavage system 1. Beyond its canonical role, a nuclear-localized fraction of the 2-oxoglutarate dehydrogenase complex containing DLD associates with histone acetyltransferase KAT2A to provide succinyl-CoA for histone succinylation, suggesting a role in epigenetic regulation 6. In monomeric form, DLD may possess serine protease activity 7. Mutations in DLD cause dihydrolipoamide dehydrogenase deficiency, a rare mitochondrial disease affecting energy metabolism and resulting in neurological complications. The DLD gene spans approximately 20 kb with 14 exons and contains multiple promoter elements including Sp1 and nuclear respiratory factor 1 binding sites 8.