Argininosuccinase

Enzyme involved in the urea cycle

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Identifiers
EC number	4.3.2.1
CAS number	9027-25-0
Alt. names
IntEnz	IntEnz view
BRENDA	BRENDA entry
ExPASy	NiceZyme view
KEGG	KEGG entry
MetaCyc	metabolic pathway

Argininosuccinase, also known as argininosuccinate lyase, is an enzyme that plays a crucial role in the urea cycle, which is a series of biochemical reactions that occur in the liver to convert ammonia into urea for excretion. This enzyme catalyzes the reversible breakdown of argininosuccinate into arginine and fumarate.

Function

Argininosuccinase is essential for the proper functioning of the urea cycle. The urea cycle is responsible for removing excess nitrogen from the body, which is primarily derived from the breakdown of amino acids. The enzyme's activity ensures that arginine is produced, which is then converted into urea and ornithine by the action of arginase.

Structure

Argininosuccinase is a homotetramer, meaning it is composed of four identical subunits. Each subunit contains an active site where the substrate, argininosuccinate, binds and is converted into arginine and fumarate. The enzyme's structure is crucial for its function, as it allows the proper alignment of the substrate for catalysis.

Genetics

The gene encoding argininosuccinase is located on chromosome 7 in humans. Mutations in this gene can lead to a condition known as argininosuccinic aciduria, a rare inherited disorder that results in the accumulation of argininosuccinate in the blood and urine. This condition can cause a variety of symptoms, including developmental delay, liver dysfunction, and hyperammonemia.

Clinical Significance

Deficiency of argininosuccinase activity leads to argininosuccinic aciduria, which is part of a group of disorders known as urea cycle disorders. These disorders can result in the accumulation of toxic levels of ammonia in the blood, leading to neurological damage and other serious health issues. Treatment often involves dietary management to limit ammonia production and the use of medications to remove excess ammonia from the body.

Also see

• Urea cycle
• Argininosuccinic aciduria
• Arginase
• Ornithine transcarbamylase