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Pathway Description
Hyperlysinemia I, Familial
Homo sapiens
Disease Pathway
Hyperlysinemia type I is a rare inherited inborn error of metabolism (IEM) of lysine metabolism. It is an autosomal recessive disorder that is caused by a defect in the alpha-aminoadipic semialdehyde synthase gene (AASS). The AASS gene encodes a bifunctional enzyme that contains lysine alpha-ketoglutarate reductase and saccharopine dehydrogenase. In hyperlysinemia type I, both enzymatic functions of AASS are defective. AASS is involved in the first two steps of the lysine degradation pathway. Lysine-alpha-ketoglutarate reductase catalyzes the metabolism of lysine to saccharopine, which is then cleaved to alpha-aminoadipic semialdehyde and glutamic acid by saccharopine dehydrogenase. Hyperlysinemia type I is characterized by elevated blood levels of the amino acid lysine, a building block of most proteins. Pipecolic acid can also be increased in serum and urine, while ornithine is typically decreased. Clinical symptoms of hyperlysinemia are highly variable. The descriptions range from symptom-free to severe developmental delay, spastic diplegia, seizures, rigidity, coma, episodic vomiting, and diarrhea. For the vast majority of people, hyperlysinemia typically causes no health problems, and most people with elevated lysine levels are unaware that they have this condition.
References
Hyperlysinemia I, Familial References
[Metagen: HYPERLYSINEMIA I, FAMILIAL](http://metagene.de/program/d.prg?id_d=212)
[OMIM: 238700](http://omim.org/entry/238700})
[NIH](http://ghr.nlm.nih.gov/condition/hyperlysinemia)
Dancis J, Hutzler J, Woody NC, Cox RP: Multiple enzyme defects in familial hyperlysinemia. Pediatr Res. 1976 Jul;10(7):686-91. doi: 10.1203/00006450-197607000-00011.
Pubmed: 934735
Nguyen TV, Andresen BS, Corydon TJ, Ghisla S, Abd-El Razik N, Mohsen AW, Cederbaum SD, Roe DS, Roe CR, Lench NJ, Vockley J: Identification of isobutyryl-CoA dehydrogenase and its deficiency in humans. Mol Genet Metab. 2002 Sep-Oct;77(1-2):68-79.
Pubmed: 12359132
Lysine Degradation References
Lehninger, A.L. Lehninger principles of biochemistry (4th ed.) (2005). New York: W.H Freeman.
Salway, J.G. Metabolism at a glance (3rd ed.) (2004). Alden, Mass.: Blackwell Pub.
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