Pyrimidine Synthesis Overview
10 Questions
1 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the regulated step in pyrimidine metabolism?

  • Synthesis of carbamoyl phosphate from glutamine and CO2 (correct)
  • Oxidation of dihydroorotate to orotic acid
  • Formation of dihydroorotate from carbamoylaspartate
  • Conversion of orotic acid to uridine monophosphate
  • Which enzyme is responsible for catalyzing the formation of orotic acid?

  • Dihydroorotate dehydrogenase (correct)
  • Carbamoyl phosphate synthetase II
  • UMP synthase
  • Aspartate transcarbamoylase
  • Which of the following regulators activates CPS II?

  • UTP
  • Aspartate
  • Glutamine
  • PRPP (correct)
  • What is a characteristic of the enzyme UMP synthase?

    <p>It is a bifunctional enzyme.</p> Signup and view all the answers

    What is the primary consequence of a deficiency in UMP synthase activity?

    <p>Orotic acid in the urine</p> Signup and view all the answers

    Which substance is NOT required for both purine and pyrimidine synthesis?

    <p>Tyrosine</p> Signup and view all the answers

    What can serve as a precursor to acetyl CoA?

    <p>β-alanine</p> Signup and view all the answers

    Which enzyme is associated with the inner mitochondrial membrane?

    <p>Dihydroorotate dehydrogenase</p> Signup and view all the answers

    What is produced as a final end product of pyrimidine nucleotide metabolism?

    <p>Urea</p> Signup and view all the answers

    What is the first product formed in the pyrimidine synthesis pathway?

    <p>Carbamoylaspartate</p> Signup and view all the answers

    Study Notes

    Pyrimidine Synthesis

    • Carbamoyl Phosphate Synthesis: The first step in pyrimidine synthesis is the creation of carbamoyl phosphate from glutamine and CO2, catalyzed by carbamoyl phosphate synthetase (CPS) II. This is the regulated step in mammalian cells.
    • CPS II Regulation: CPS II is inhibited by UTP (the end product of this pathway), and is activated by PRPP (5-phosphoribosyl 1-pyrophosphate).
    • Orotic Acid Synthesis: The second step is the formation of carbamoylaspartate, catalyzed by aspartate transcarbamoylase. The pyrimidine ring is formed through a hydrolytic reaction catalyzed by dihydroorotase. This then produces dihydroorotate, which is oxidized to orotic acid.
    • Dihydroorotate Dehydrogenase: The enzyme that converts dihydroorotate to orotic acid is called dihydroorotate dehydrogenase and is found in the inner mitochondrial membrane.
    • Cytosolic Enzyme Location: All other enzymes involved in pyrimidine biosynthesis are located in the cytosol.
    • Orotidine 5'-monophosphate (OMP) Synthesis: Orotic acid is converted into the nucleotide OMP, the parent pyrimidine mononucleotide, using PRPP as the ribose 5-phosphate donor.
    • Uridine Monophosphate (UMP) Synthesis: OMP is then converted to UMP by a bifunctional enzyme called UMP synthase.

    Pyrimidine Degradation

    • Urea Cycle: Urea is the final product of pyrimidine degradation.
    • β-alanine and β-aminoisobutyrate: These are byproducts of pyrimidine degradation and can be used as precursors for acetyl CoA and succinyl CoA, respectively.
    • Krebs Cycle: β-alanine and β-aminoisobutyrate play a role in the Krebs cycle.

    Orotic Aciduria

    • Genetic Defect: Orotic aciduria is a rare genetic disorder caused by a deficiency in the bifunctional enzyme UMP synthase.
    • Symptoms: This deficiency leads to an accumulation of orotic acid in the urine, resulting in poor growth and megaloblastic anemia.

    Studying That Suits You

    Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

    Quiz Team

    Related Documents

    Description

    Explore the key steps involved in pyrimidine synthesis, focusing on carbamoyl phosphate synthesis and the role of various enzymes. Understand the regulation of CPS II and the conversion of dihydroorotate to orotic acid. This quiz covers vital concepts in biochemistry and metabolism.

    More Like This

    Synthèse des ribonucléotides pyrimidiques
    22 questions
    Biochemistry Purine and Pyrimidine Metabolism
    24 questions
    Nucleotide Metabolism and Synthesis
    10 questions
    Use Quizgecko on...
    Browser
    Browser