Saccharopinuria is a metabolic disorder caused by a defect in a bifunctional protein with lysine-ketoglutarate reductase (LKR) activity and saccharopine dehydrogenase (SDH) activity, aminoadipic semialdehyde synthase (AASS), which catalyzes the first two steps in the lysine-degradation pathway. Patients with this disorder have both hyperlysinemia and saccharopinuria, although the saccharopinuria is much more severe. It seems likely that this disorder results from specific mutations in the portion of AASS encoding SDH, which could explain the high levels of saccharopine, compared with that in patients with hyperlysinemia [DS:H00188].
