Genetic Diseases : Autosomal recessive diseases

 

 

   The urea cycle is a sequence of chemical reactions that take place in the liver. During this process, excess nitrogen (which is formed when the body uses protein) is excreted from the body, and a substance called urea is formed (it is excreted from the body through the kidneys). There are two types of citrulinemia.

 

    Type I citrulinemia

 

  In the OMIM information database, this disease is listed under the number 215700, its other name is classic citrulinemia. The disease usually manifests itself in the first days of life, often at birth. Affected children may seem normal, but with the accumulation of ammonia in the body, patients become lethargic, lose their appetite, vomit, have seizures and sometimes lose consciousness. These disorders can often be life-threatening. More mild symptoms of the disease occur more often in adulthood, less often in childhood. In some people with a gene mutation that causes citrulinemia type I, the signs and symptoms of the disease are not noticeable. 

 

   Type I citrulinemia is the most common genetic disorder (compared to other types of citrulinemia), which is detected in 1 child in 57,000 newborns worldwide. The disease is caused by mutations in the ASS gene.

 

     Argininosuccinate synthetase (ES 6.3.4.5) is an enzyme whose production is encoded by this gene. It is responsible for one stage of the urea cycle. Mutations in the ASS gene reduce the activity of the enzyme, which, accordingly, disrupts the urea cycle, and this, in turn, prevents the effective excretion of excess nitrogen from the body. Excess nitrogen in the form of ammonia and other by-products of the urea cycle accumulate in the blood, which leads to the appearance of signs characteristic of type I citrulinemia.