Adenylosuccinate lyase

Adenylosuccinate lyase

Active sites of adenylosuccinate lyase

Adenylosuccinate lyase (ASL) is an enzyme that plays a crucial role in the purine biosynthesis pathway. It catalyzes two distinct reactions in the de novo synthesis of purine nucleotides, which are essential for the production of adenosine triphosphate (ATP), guanosine triphosphate (GTP), and other important biomolecules.

Function

Adenylosuccinate lyase is responsible for two key reactions in purine metabolism:

1. The conversion of adenylosuccinate to adenosine monophosphate (AMP) and fumarate. 2. The conversion of 5-aminoimidazole-4-(N-succinylcarboxamide) ribonucleotide (SAICAR) to 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR) and fumarate.

These reactions are part of the purine nucleotide cycle, which is essential for the synthesis of purine nucleotides and the regulation of energy metabolism in cells.

Structure

Adenylosuccinate lyase is a homotetrameric enzyme, meaning it is composed of four identical subunits. Each subunit contains an active site where the substrate binds and the reaction takes place. The enzyme's structure allows it to facilitate the cleavage of the carbon-nitrogen bond in its substrates, leading to the formation of AMP and fumarate or AICAR and fumarate.

Mechanism

Reaction mechanism of adenylosuccinate lyase

The reaction mechanism of adenylosuccinate lyase involves the formation of a covalent intermediate between the enzyme and the substrate. This intermediate is then cleaved to release the products. The enzyme utilizes a general acid-base catalysis mechanism, where specific amino acid residues in the active site act as proton donors and acceptors to facilitate the reaction.

Clinical significance

Deficiencies in adenylosuccinate lyase activity can lead to a rare metabolic disorder known as adenylosuccinate lyase deficiency. This condition is characterized by the accumulation of adenylosuccinate and SAICAR in tissues and bodily fluids, leading to a range of symptoms including developmental delay, seizures, and autistic features. The disorder is inherited in an autosomal recessive manner.

Related pages

• Purine metabolism
• Adenylosuccinate synthetase
• Adenosine monophosphate
• Fumarate

Gallery

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  Purine biosynthesis pathway
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  Overall reactions catalyzed by adenylosuccinate lyase

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  Active sites of adenylosuccinate lyase
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  Purine biosynthesis pathway
• 
  Overall reactions catalyzed by adenylosuccinate lyase
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  Reaction mechanism of adenylosuccinate lyase