Saccharopinuria

Saccharopinuria
Synonyms	Hyperlysinemia type II<ref> Orphanet: Saccharopinuria(link). www.orpha.net. </ref>
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Saccharopinuria (an excess of saccharopine in the urine), also called saccharopinemia, saccharopine dehydrogenase deficiency or alpha-aminoadipic semialdehyde synthase deficiency,<ref name=omim>Online Mendelian Inheritance in Man (OMIM) 268700 </ref> is a variant form of hyperlysinemia.<ref>,

 Saccharopinuria (a variant form of familial hyperlysinemia), 
 Ryoikibetsu Shokogun Shirizu, 
 1998,
 
 pp. 191–194,
 
 PMID: 9590025,</ref> It is caused by a partial deficiency of the enzyme saccharopine dehydrogenase, which plays a secondary role in the lysine metabolic pathway. Inheritance is thought to be autosomal recessive, but this cannot be established as individuals affected by saccharopinuria typically have only a 40% reduction in functional enzyme.<ref name=omim/>

Saccharopinuria is a disorder of lysine metabolism associated with hyperlysinaemia and lysinuria.

Epidemiology

The prevalence is unknown.

Cause

It is caused by a deficiency in the bifunctional enzyme alpha-aminoadipate semialdehyde synthase, encoded by the AASS gene (located at 7q31.3). This enzyme has both lysine-ketoglutarate reductase (LKR) and saccharopine dehydrogenase (SDH) activity, and catalyses the first two steps of lysine degradation. In saccharopinuria, deficiency of the LKR activity is only partial.

Inheritance

Autosomal recessive inheritance, a 25% chance

Saccharopinuria is an autosomal recessive disorder.

Signs and symptoms

The few patients with saccharopinuria have been investigated largely because of neurological problems including spastic diplegia but the relationship between the saccharopinuria and these is unclear.

Alternate names

Saccharopine dehydrogenase deficiency

See also

• Hyperlysinemia

External links

• Saccharopinuria; Alpha-aminoadipic semialdehyde synthase deficiency at NIH's Office of Rare Diseases

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NIH genetic and rare disease info

• NIH info on Saccharopinuria

Saccharopinuria is a rare disease.

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