biology

Phosphoribosylaminoimidazolesuccinocarboxamide synthase

Phosphoribosylaminoimidazolesuccinocarboxamide synthase is a biology topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Phosphoribosylaminoimidazolesuccinocarboxamide synthase rather than just read about it. In short: In molecular biology, the protein domain SAICAR synthase is an enzyme which catalyses a reaction to create SAICAR. In enzymology, this enzyme is also known as phosphoribosylaminoimidazolesuccinocarboxamide synthase (EC 6.3.2.6).

Key takeaways

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Reference excerpt

In molecular biology, the protein domain SAICAR synthase is an enzyme which catalyses a reaction to create SAICAR. In enzymology, this enzyme is also known as phosphoribosylaminoimidazolesuccinocarboxamide synthase (EC 6.3.2.6). It is an enzyme that catalyzes the chemical reaction

ATP + 5-amino-1-(5-phospho-D-ribosyl)imidazole-4-carboxylate + L-aspartate ⇌ {\displaystyle \rightleftharpoons } ADP + phosphate + (S)-2-[5-amino-1-(5-phospho-D-ribosyl)imidazole-4-carboxamido]succinate The 3 substrates of this enzyme are ATP, 5-amino-1-(5-phospho-D-ribosyl)imidazole-4-carboxylate, and L-aspartate, whereas its 3 products are ADP, phosphate, and (S)-2-[5-amino-1-(5-phospho-D-ribosyl)imidazole-4-carboxamido]succinate. This enzyme belongs to the family of ligases, to be specific those forming carbon-nitrogen bonds as acid-D-amino-acid ligases (peptide synthases). The systematic name of this enzyme class is 5-amino-1-(5-phospho-D-ribosyl)imidazole-4-carboxylate:L-aspartate ligase (ADP-forming). This enzyme participates in purine metabolism. This particular protein family is of huge importance as it is found in all three domains of life. It is the seventh step in the pathway of purine biosynthesis. Purines are vital to all cells as they are involved in energy metabolism and DNA synthesis. Furthermore, they are of specific interest to scientific researchers as the study of the purine biosynthesis pathway could lead to the development of chemotherapeutic drugs. This is because most cancers lack a salvage pathway for adenine nucleotides and rely entirely on the SAICAR pathway.

Protein domain This protein domain is found in eukaryotes, bacteria and archaea. It is vital for living organisms since it catalyses a step in the purine biosynthesis pathway which aids energy metabolism and DNA synthesis.

Protein domain function In bacteria and plants this protein domain only catalyses the synthesis of SAICAR. However, in mammals it also catalyses phosphoribosylaminoimidazole carboxylase (AIRC) activity.

Protein domain structure This particular protein is an octamer made up of 8 identical subunits. Each monomer consists of a central domain and a C-terminal alpha helix. The central domain consists of a five-stranded parallel beta sheet flanked by three alpha helices one side of the sheet and two alpha helices on the other, forming a three-layer (alpha beta alpha) sandwich.

Structural studies As of late 2007, 10 structures have been solved for this class of enzymes, with PDB accession codes PDB: 1A48, PDB: 1KUT, PDB: 1OBD, PDB: 1OBG, PDB: 2CNQ, PDB: 2CNU, PDB: 2CNV, PDB: 2GQR, PDB: 2GQS, and PDB: 2H31.

Other common names phosphoribosylaminoimidazole-succinocarboxamide synthetase, PurC, SAICAR synthetase, 4-(N-succinocarboxamide)-5-aminoimidazole synthetase, 4-[(N-succinylamino)carbonyl]-5-aminoimidazole ribonucleotide, synthetase, SAICARs, phosphoribosylaminoimidazolesuccinocarboxamide synthetase, 5-aminoimidazole-4-N-succinocarboxamide ribonucleotide synthetase.

References

LUKENS LN, BUCHANAN JM (1959). "Biosynthesis of the purines. XXIV. The enzymatic synthesis of 5-amino-1-ribosyl-4-imidazolecarboxylic acid 5'-phosphate from 5-amino-1-ribosylimidazole 5'-phosphate and carbon dioxide". J. Biol. Chem. 234 (7): 1799–805. doi:10.1016/S0021-9258(18)69929-6. PMID 13672967. Parker J (1984). "Identification of the purC gene product of Escherichia coli". J. Bacteriol. 157 (3): 712–7. doi:10.1128/JB.157.3.712-717.1984. PMC 215316. PMID 6365889. Ebbole DJ, Zalkin H (1987). "Cloning and characterization of a 12-gene cluster from Bacillus subtilis encoding nine enzymes for de novo purine nucleotide synthesis". J. Biol. Chem. 262 (17): 8274–87. doi:10.1016/S0021-9258(18)47560-6. PMID 3036807. Chen ZD, Dixon JE, Zalkin H (1990). "Cloning of a chicken liver cDNA encoding 5-aminoimidazole ribonucleotide carboxylase and 5-aminoimidazole-4-N-succinocarboxamide ribonucleotide synthetase by functional complementation of Escherichia coli pur mutants". Proc. Natl. Acad. Sci. U.S.A. 87 (8): 3097–101. Bibcode:1990PNAS...87.3097C. doi:10.1073/pnas.87.8.3097. PMC 53841. PMID 1691501. O'Donnell AF, Tiong S, Nash D, Clark DV (2000). "The Drosophila melanogaster ade5 gene encodes a bifunctional enzyme for two steps in the de novo purine synthesis pathway". Genetics. 154 (3): 1239–53. doi:10.1093/genetics/154.3.1239. PMC 1460979. PMID 10757766. Nelson SW, Binkowski DJ, Honzatko RB, Fromm HJ (2005). "Mechanism of action of Escherichia coli phosphoribosylaminoimidazolesuccinocarboxamide synthetase". Biochemistry. 44 (2): 766–74. doi:10.1021/bi048191w. PMID 15641804. S2CID 41673787.

Illustrations

Worked examples

Example 1 — a first encounter with Phosphoribosylaminoimidazolesuccinocarboxamide synthase

Start with the simplest possible case. Write down what Phosphoribosylaminoimidazolesuccinocarboxamide synthase claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Phosphoribosylaminoimidazolesuccinocarboxamide synthase before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Phosphoribosylaminoimidazolesuccinocarboxamide synthase ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Phosphoribosylaminoimidazolesuccinocarboxamide synthase

In research: Phosphoribosylaminoimidazolesuccinocarboxamide synthase appears in biology research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Phosphoribosylaminoimidazolesuccinocarboxamide synthase in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Phosphoribosylaminoimidazolesuccinocarboxamide synthase is common in secondary-school and first-year university syllabi. It links to neighbouring topics EC 6.3.2, Enzymes of known structure, Ligase stubs, so understanding it makes those chapters shorter.
In everyday life: Look for Phosphoribosylaminoimidazolesuccinocarboxamide synthase outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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Frequently asked questions

What is Phosphoribosylaminoimidazolesuccinocarboxamide synthase in simple terms?

Why does Phosphoribosylaminoimidazolesuccinocarboxamide synthase matter?

Because it connects several biology ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

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Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Phosphoribosylaminoimidazolesuccinocarboxamide synthase.