Sulfate Conjugation in Biochemistry
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Questions and Answers

What plays a crucial role in the formation of GSH conjugates of electrophilic xenobiotics or metabolites?

  • Xenobiotic metabolizing enzymes
  • Electrophilic enzymes
  • Mercapturic acid enzymes
  • GSH S-transferases (correct)
  • What is the product of the conjugation reaction between GSH and electrophilic xenobiotics or metabolites?

  • GSH conjugates
  • Xenobiotic metabolites
  • Electrophilic acids
  • Mercapturic acids (correct)
  • What type of xenobiotics or metabolites undergo conjugation with GSH?

  • Inactive
  • Nucleophilic
  • Reactive
  • Electrophilic (correct)
  • What is the role of GSH S-transferases in the conjugation reaction?

    <p>To catalyze the conjugation of GSH with electrophilic xenobiotics or metabolites</p> Signup and view all the answers

    What is the result of the conversion of GSH conjugates of electrophilic xenobiotics or metabolites?

    <p>Formation of mercapturic acids</p> Signup and view all the answers

    Which of the following compounds is not a primary amino group, but can still undergo acetylation?

    <p>Quaternary ammonium compounds</p> Signup and view all the answers

    What is the functional group that undergoes acetylation in primary aromatic amines?

    <p>ArNH2</p> Signup and view all the answers

    Which of the following statements is true about the acetylation of hydrazines?

    <p>It is a specific reaction to primary amino groups</p> Signup and view all the answers

    What is the general term for the functional group that undergoes acetylation in sulfonamides?

    <p>Primary amino group</p> Signup and view all the answers

    Which of the following compounds can undergo acetylation due to the presence of a primary amino group?

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

    What is the primary functional group that undergoes sulfation in sulfate conjugation?

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

    Which of the following compounds is NOT a common substrate for sulfation?

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

    What is the primary step in the sulfate conjugation process?

    <p>Activation of inorganic sulfate to PAPS</p> Signup and view all the answers

    Which of the following is the order of preference for sulfation?

    <p>Phenols &gt; Alcohols &gt; Aromatic amines &gt; N-hydroxyl</p> Signup and view all the answers

    Which of the following is a characteristic of sulfate conjugation?

    <p>It is a less frequent conjugation method than glucuronidation</p> Signup and view all the answers

    What is the role of PAPS in sulfate conjugation?

    <p>It is the activated form of inorganic sulfate</p> Signup and view all the answers

    What is the result of the process involving γ-glutamylcysteine}

    <p>Formation of S-substituted cysteine residue</p> Signup and view all the answers

    What is the product of the reaction involving glutathione?

    <p>Glutathione adduct</p> Signup and view all the answers

    What is the outcome of the enzymatic cleavage of two amino acids?

    <p>Removal of glutamic acid and glycine</p> Signup and view all the answers

    What is the purpose of N-acetylation in this process?

    <p>To stabilize the S-substituted cysteine residue</p> Signup and view all the answers

    What is the intermediate formed in the process involving γ-glutamylcysteine?

    <p>Glutathione adduct</p> Signup and view all the answers

    What is the final product of the process involving γ-glutamylcysteine?

    <p>N-acetylated S-substituted cysteine residue</p> Signup and view all the answers

    What is the result of regioselective O-demethylation of the 4-OCH3 group in papaverine?

    <p>Formation of an alcohol</p> Signup and view all the answers

    What has changed significantly in recent years regarding drug metabolites?

    <p>The traditional idea of drug metabolites being inactive</p> Signup and view all the answers

    What is the current understanding of pharmacologically active metabolites?

    <p>They are sometimes active and significant</p> Signup and view all the answers

    What is the name of the process by which the 4-OCH3 group in papaverine is converted to an alcohol?

    <p>Regioselective O-demethylation</p> Signup and view all the answers

    What is the significance of pharmacologically active metabolites in drug therapy?

    <p>They are sometimes a desired outcome of drug treatment</p> Signup and view all the answers

    What is the implication of increasing evidence on pharmacologically active metabolites?

    <p>Drug metabolites are sometimes active and significant</p> Signup and view all the answers

    Study Notes

    Sulfate Conjugation

    • Sulfate conjugation (sulfation) is less frequent compared to glucuronide conjugation (glucuronidation)
    • The most common functional groups that undergo sulfation are free OH, NH2, and NHOH
    • Phenols (Ph-OH) are the main group of substrates that undergo sulfate conjugation, followed by:
    • Alcohols (ROH)
    • Aromatic amines (ph-NH)
    • N-hydroxyl (N-OH)

    Substrates of Sulfate Conjugation

    • Sulfation is used to conjugate endogenous compounds, including:
    • Steroids
    • Heparin
    • Chondroitin
    • Catecholamines
    • Thyroxine

    Sulfate Conjugation Process

    • The process involves the activation of inorganic sulfate (SO4) to form CoEnzyme 3′-phosphoadenosine-5′-phosphosulfate (PAPS)

    GSH Conjugation

    • Formation of GSH conjugates of electrophilic xenobiotics or metabolites (E) occurs through enzymatic cleavage of two amino acids (glutamic acid and glycine) from the formed GSH adduct
    • Subsequent N-acetylation of the remaining S-substituted cysteine residue forms mercapturic acids
    • Conjugation of substrates with GSH is catalyzed by enzymes known as GSH S-transferases

    Acetylation

    • The functional group undergoing acetylation is the primary amino group (NH2), including:
    • Primary aromatic amines (ArNH2)
    • Sulfonamides (H2NC6H4SO2NHR)
    • Hydrazines (-NHNH2)

    Pharmacologically Active Metabolites

    • The traditional idea that drug metabolites are inactive and insignificant in drug therapy has changed dramatically in recent years
    • Evidence suggests that many drugs undergo biological transformation, leading to pharmacologically active metabolites

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