Aminoadipate-semialdehyde synthase (AASS) is a bifunctional enzyme catalyzing the first two steps of lysine degradation via the saccharopine pathway. It possesses both lysine-ketoglutarate reductase and saccharopine dehydrogenase activities. Mutations in the AASS gene cause familial hyperlysinemia, a rare autosomal recessive disorder characterized by elevated plasma lysine levels, though clinical manifestations are typically benign. AASS dysfunction disrupts mitochondrial energy metabolism and amino acid homeostasis. Beyond its metabolic role, emerging evidence suggests AASS may influence cellular redox status and autophagy regulation, positioning it as a potential therapeutic target for metabolic disorders and lysine-related pathologies (PMID: 41158987; 10775527).