10 Questions
What is the key enzyme responsible for generating phosphoribosyl pyrophosphate (PRPP) in De Novo Purine Synthesis?
PRPP synthetase
What is the primary function of the Purine Salvage Pathway?
To recycle free purine bases to form nucleotides
What is the role of adenosine deaminase in Adenosine Metabolism?
Deaminates adenosine to inosine
What is the key enzyme responsible for converting AMP to ADP and ATP in the Purine Nucleotide Cycle?
Adenylate kinase
What is the primary function of Xanthine Oxidase in purine metabolism?
To convert hypoxanthine to xanthine and xanthine to uric acid
What is the key enzyme inhibited by allopurinol in the treatment of gout?
Xanthine Oxidase
What is the genetic disorder caused by a deficiency of hypoxanthine-guanine phosphoribosyltransferase?
Lesch-Nyhan syndrome
What is the product of the reaction catalyzed by Glutamine phosphoribosyl pyrophosphate amidotransferase in De Novo Purine Synthesis?
IMP
What is the primary function of the enzyme Adenosine kinase in Adenosine Metabolism?
Converts adenosine to AMP
What is the genetic disorder characterized by immunodeficiency and increased susceptibility to infections due to a deficiency of adenosine deaminase?
Adenosine deaminase deficiency
Study Notes
De Novo Purine Synthesis
- Occurs in the cytosol of cells
- Two stages: synthesis of inosine monophosphate (IMP) and conversion of IMP to AMP and GMP
- Key enzymes:
- PRPP synthetase (generates phosphoribosyl pyrophosphate (PRPP))
- Glutamine phosphoribosyl pyrophosphate amidotransferase (converts PRPP to IMP)
- Regulation: feedback inhibition by AMP and GMP, allosteric inhibition by ATP
Purine Salvage Pathway
- Recycles free purine bases (adenine, guanine, and hypoxanthine) to form nucleotides
- Two key enzymes:
- Adenosine kinase (converts adenine to AMP)
- Hypoxanthine-guanine phosphoribosyltransferase (converts hypoxanthine and guanine to IMP and GMP, respectively)
- Importance: conserves energy and reduces the need for de novo synthesis
Adenosine Metabolism
- Adenosine is a signaling molecule involved in various physiological processes
- Metabolism:
- Deaminated to inosine by adenosine deaminase
- Converted to AMP by adenosine kinase
- Broken down to inosine and ammonia by adenosine deaminase
- Importance: adenosine receptor signaling plays a role in regulating cardiac function, pain perception, and inflammation
Purine Nucleotide Cycle
- A metabolic pathway that interconverts AMP, ADP, and ATP
- Key enzymes:
- Adenylate kinase (converts AMP to ADP and ATP)
- Adenosine monophosphate deaminase (converts AMP to IMP)
- Importance: regulates the balance of adenine nucleotides in cells
Xanthine Oxidase Function
- A key enzyme in the degradation of purines to uric acid
- Catalyzes the oxidation of hypoxanthine to xanthine and xanthine to uric acid
- Inhibition: allopurinol (used to treat gout and hyperuricemia)
Disorders of Purine Metabolism
- Gout: Characterized by hyperuricemia, uric acid crystal deposition, and joint inflammation
- Lesch-Nyhan syndrome: A genetic disorder caused by a deficiency of hypoxanthine-guanine phosphoribosyltransferase, leading to excess uric acid production and neurological symptoms
- Adenosine deaminase deficiency: A genetic disorder characterized by immunodeficiency and increased susceptibility to infections
- Purine nucleoside phosphorylase deficiency: A genetic disorder characterized by immunodeficiency and neurological symptoms
This quiz covers the processes of de novo purine synthesis and the purine salvage pathway, including key enzymes and regulation mechanisms.
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