SAICAR

SAICAR (Succinylaminoimidazolecarboxamide ribotide) is a molecule that plays a crucial role in the biochemical processes of cells. It is an intermediate in the purine biosynthesis pathway, a metabolic pathway that leads to the formation of adenine and guanine from simple molecules.

Structure and Properties[edit | edit source]

File:SAICAR structure.png

Chemical structure of SAICAR

SAICAR is a ribonucleotide, which means it contains a ribose sugar, an aminoimidazolecarboxamide base, and a phosphate group. The ribose sugar is attached to the base at the 1' position and to the phosphate group at the 5' position. The base contains an imidazole ring and a carboxamide group, which are responsible for the molecule's ability to participate in various biochemical reactions.

Role in Purine Biosynthesis[edit | edit source]

In the purine biosynthesis pathway, SAICAR is synthesized from phosphoribosylaminoimidazolesuccinocarboxamide (PAIS) by the enzyme SAICAR synthetase. This reaction also involves the input of an ATP molecule, which is converted to ADP.

SAICAR is then converted to aminoimidazole carboxamide ribonucleotide (AICAR) by the enzyme adenylosuccinate lyase. This reaction releases a molecule of fumarate, which can be used in the citric acid cycle.

Clinical Significance[edit | edit source]

Mutations in the gene encoding SAICAR synthetase can lead to a rare disorder known as SAICAR synthetase deficiency. This condition is characterized by a buildup of SAICAR in the body, which can lead to various symptoms including developmental delay, seizures, and failure to thrive.