Nucleotide Metabolism - Purine Nucleotide Synthesis

These flashcards cover key concepts and processes linked to purine nucleotide metabolism for exam preparation.

What are the common purine bases?

Adenine (Ade) and Guanine (Gua)

What are the common pyrimidine bases?

Cytosine (Cyt), Uracil (Ura), and Thymine (Thy)

What is a nucleoside?

A nucleoside is comprised of a ribose or deoxyribose linked to a base.

What is a nucleotide?

A nucleotide is a nucleoside phosphate (mono-, di-, tri-).

What is the primary energy source nucleotide?

ATP (Adenosine triphosphate)

Which nucleotide is used in protein synthesis?

GTP (Guanosine triphosphate)

What nucleotide is involved in activating glucose and galactose?

UTP (Uridine triphosphate)

What is the role of CTP in metabolism?

CTP is involved in (phospho)lipid metabolism.

What is the key role of AMP?

AMP is part of NAD and coenzyme A.

What are the two types of pathways for nucleotide synthesis?

De novo synthesis and salvage pathways.

What does de novo synthesis start with?

Metabolic precursors such as amino acids, ribose 5-phosphate, CO2, and NH3.

What is the function of salvage pathways in nucleotide metabolism?

They recycle free bases and nucleosides released by nucleic acid breakdown.

Where is purine synthesis primarily located?

In the liver.

What are the parent purine nucleotides produced in de novo synthesis?

Adenosine 5ʹ-monophosphate (AMP) and Guanosine 5ʹ-monophosphate (GMP).

What is the first step in de novo synthesis of purines?

Synthesis of 5-phosphoribosyl 1-pyrophosphate (PRPP) from ribose-5-phosphate.

Which enzyme catalyzes the synthesis of PRPP?

PRPP synthase.

What triggers the formation of 5-phosphoribosylamine from PRPP?

The attachment of an N atom from glutamine.

How is glycinamide ribonucleotide formed in nucleotide synthesis?

By the addition of 3 atoms from glycine via phosphoribosylglycinamide synthetase.

What is formylglycinamide ribonucleotide?

It is formed by the formylation of glycinamide ribonucleotide.

What forms 5-aminoimidazole ribonucleotide (AIR)?

Dehydration and ring closure of formylglycinamide ribonucleotide.

What is the role of aspartate in purine synthesis?

Aspartate donates its amino group during the synthesis process.

What is inosinate (IMP)?

It is the first complete intermediate in purine de novo synthesis.

How is AMP formed from IMP?

By inserting –NH2 from aspartate into IMP to form adenylosuccinate.

What enzyme converts IMP to GMP?

IMP dehydrogenase.

What regulates de novo synthesis of nucleotides?

The concentration of PRPP and the activity of enzymes like PRPP synthase.

Which condition is characterized by high levels of uric acid in the blood?

Gout.

What causes Lesch-Nyhan syndrome?

A virtually complete deficiency of HGPRT.

What genetic disorder leads to severe combined immunodeficiency disease (SCID)?

Adenosine deaminase (ADA) deficiency.

What does the absence of ADA lead to in T and B lymphocytes?

A lack of proper development and increased dATP levels.

What is the consequence of accumulating dATP in cells?

Inhibition of ribonucleotide reductase and general deficiency of other dNTPs.

How does xanthine oxidase deficiency manifest?

It can lead to hypouricemia and kidney issues due to increased xanthine.

What physical symptoms are associated with Gout?

Inflammation and pain in joints, often with deposits of sodium urate crystals.

What drug inhibits xanthine oxidase in gout treatment?

Allopurinol.

What is one outcome of treating gout with allopurinol?

Decreased deposition of uric acid crystals.

What type of reaction does purine salvage involve?

Phosphoribosylation of free purines.

Which enzymes are important in purine salvage pathways?

Adenine phosphoribosyltransferase (APRT) and hypoxanthine-guanine phosphoribosyltransferase (HGPRT).

What genetic defect is associated with xanthine oxidase activity?

Xanthinuria.

What dietary recommendations are given to manage gout?

Low nucleic acid diets.

What is the enzyme that catalyzes the reduction of ribonucleotides to deoxyribonucleotides?

Ribonucleotide reductase.

What characterizes hypoxanthine accumulation?

It can indicate a failure of the salvage pathway.

What type of genetic abnormality leads to hyperuricemia?

Genetic defects in PRPP synthase.

What is the medical significance of uric acid in metabolism?

It is the end product of purine catabolism in many organisms.