| SAICAR synthase | |||||||||
|---|---|---|---|---|---|---|---|---|---|
 Phosphoribosylaminoimidazole succinocarboxamide synthetase oktamer, Human | |||||||||
| Identifiers | |||||||||
| EC no. | 6.3.2.6 | ||||||||
| CAS no. | 9023-67-0 | ||||||||
| Databases | |||||||||
| IntEnz | IntEnz view | ||||||||
| BRENDA | BRENDA entry | ||||||||
| ExPASy | NiceZyme view | ||||||||
| KEGG | KEGG entry | ||||||||
| MetaCyc | metabolic pathway | ||||||||
| PRIAM | profile | ||||||||
| PDB structures | RCSB PDBPDBePDBsum | ||||||||
| Gene Ontology | AmiGO /QuickGO | ||||||||
| |||||||||
| SAICAR synthetase | |||||||||
|---|---|---|---|---|---|---|---|---|---|
 Structural genomics, protein TM1243, (SAICAR synthetase) | |||||||||
| Identifiers | |||||||||
| Symbol | SAICAR_synt | ||||||||
| Pfam | PF01259 | ||||||||
| InterPro | IPR001636 | ||||||||
| PROSITE | PDOC00810 | ||||||||
| SCOP2 | 1a48 /SCOPe /SUPFAM | ||||||||
| CDD | cd00476 | ||||||||
| |||||||||
In molecular biology, theprotein domainSAICAR synthase is an enzyme which catalyses a reaction to createSAICAR. Inenzymology, this enzyme is also known asphosphoribosylaminoimidazolesuccinocarboxamide synthase (EC6.3.2.6). It is anenzyme thatcatalyzes thechemical reaction
The 3substrates of this enzyme areATP,5-amino-1-(5-phospho-D-ribosyl)imidazole-4-carboxylate, andL-aspartate, whereas its 3products areADP,phosphate, and (S)-2-[5-amino-1-(5-phospho-D-ribosyl)imidazole-4-carboxamido]succinate.
This enzyme belongs to the family ofligases, to be specific those forming carbon-nitrogen bonds as acid-D-amino-acid ligases (peptide synthases). Thesystematic name of this enzyme class is5-amino-1-(5-phospho-D-ribosyl)imidazole-4-carboxylate:L-aspartate ligase (ADP-forming). This enzyme participates inpurine metabolism.
This particular protein family is of huge importance as it is found in all threedomains of life. It is the seventh step in the pathway ofpurine biosynthesis. Purines are vital to all cells as they are involved in energymetabolism andDNA synthesis.[1] Furthermore, they are of specific interest to scientific researchers as the study of the purine biosynthesis pathway could lead to the development ofchemotherapeutic drugs.[2] This is because mostcancers lack a salvage pathway for adenine nucleotides and rely entirely on the SAICAR pathway.[3]
This protein domain is found ineukaryotes,bacteria andarchaea. It is vital for living organisms since it catalyses a step in the purine biosynthesis pathway which aids energymetabolism andDNA synthesis.
In bacteria and plants this protein domain only catalyses the synthesis of SAICAR. However, in mammals it also catalyses phosphoribosylaminoimidazole carboxylase (AIRC) activity.[3]
This particular protein is an octamer made up of 8 identical subunits. Each monomer consists of a central domain and a C-terminalalpha helix. The central domain consistsof a five-stranded parallelbeta sheet flanked by three alpha helicesone side of the sheet and two alpha helices on the other, forming a three-layer (alpha beta alpha) sandwich.[4]
As of late 2007, 10structures have been solved for this class of enzymes, withPDB accession codes1A48,1KUT,1OBD,1OBG,2CNQ,2CNU,2CNV,2GQR,2GQS, and2H31.
