Metabolic Reactions and Cytochrome P450
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Metabolic Reactions and Cytochrome P450

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Questions and Answers

What is the product of O-dealkylation of phenacetin?

  • Analgesic
  • Naphthalene
  • Acetaminophen (correct)
  • Morphine

    • N-Dealkylation involves the removal of an alkyl group from a nitrogen atom.

    True

    What type of biological activity is associated with the product of phenacetin O-dealkylation?

    Analgesic activity

    _______ is formed from the oxidative deamination of certain nitrogen mustards in neoplastic cells.

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

    Match the following compounds with their respective structures or activities:

    <p>Alprazolam = X = H Triazolam = X = Cl Phenacetin = O-dealkylation leads to acetaminophen Phosphamide analogs = Selective activation in neoplastic cells</p> Signup and view all the answers

    Which enzyme is primarily involved in N-Dealkylation processes?

    <p>Cytochrome P450</p> Signup and view all the answers

    O-dealkylation leads to an increase in analgesic activity of the original compound.

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

    Identify the compound represented by 'X' in the N-Dealkylation products.

    <p>H or Cl</p> Signup and view all the answers

    What is the primary purpose of sulfasalazine?

    <p>For inflammatory bowel disease</p> Signup and view all the answers

    The reduction of thiamine aims to decrease its lipophilicity for better absorption into the CNS.

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

    What is the product of the azo reduction of sulfasalazine?

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

    The process involving the cleavage by bacteria in the lower _____ results in the breakdown of sulfasalazine.

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

    Match the following compounds with their functions:

    <p>Sulfasalazine = Treats inflammatory bowel disease Thiamine = Improves CNS absorption Primaquine = Targets malaria parasites GSH = Reduces disulfides</p> Signup and view all the answers

    Which of the following best describes the role of GSH in disulfide reduction?

    <p>Acts as a reducing agent</p> Signup and view all the answers

    The activation of sulfasalazine is an example of reductive activation by aerobic bacteria.

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

    What is modified to reduce the toxicity of primaquine?

    <p>macromolecular drug delivery system</p> Signup and view all the answers

    What is essential for the activation of cyclophosphamide?

    <p>Liver homogenates</p> Signup and view all the answers

    Cyclophosphamide activates without the involvement of liver homogenates.

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

    What chemical process is illustrated by the presence of phosphoramidase?

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

    Cyclophosphamide required __________ in order to become effective.

    <p>liver homogenates</p> Signup and view all the answers

    Match the following compounds with their associated characteristics:

    <p>Cyclophosphamide = Requires liver homogenates for activation P-450 = Enzyme responsible for drug metabolism Phosphoramidase = Catalyzes hydrolysis DNA = Contains genetic information</p> Signup and view all the answers

    Which of the following is a characteristic of P-450?

    <p>It helps metabolize drugs in the liver.</p> Signup and view all the answers

    Cyclophosphamide can function without hydrolysis.

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

    What are the resultant compounds when cyclophosphamide undergoes hydrolysis?

    <p>Active metabolites</p> Signup and view all the answers

    What is the therapeutic index of the compound 8.116 compared to 8.115 in mice?

    <p>12 times higher</p> Signup and view all the answers

    The chemical formula for __________ is associated with the components of cyclophosphamide activation.

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

    Match the following values with their relevance in the context:

    <p>8.80 = Cyclophosphamide component 8.81 = Cyclophosphamide component 8.82 = Involved in phosphoramidase activity 8.84 = Hydrolysis process</p> Signup and view all the answers

    Acyclovir has an absorption rate of 50-60%.

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

    Which drug is used as an anti-leukemia treatment?

    <p>6-mercaptopurine</p> Signup and view all the answers

    The compound that improves uptake in the liver is _____ .

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

    Match the following drugs to their effects or characteristics:

    <p>Primaquine = Antimalarial with selective reduction inside the cell 6-mercaptopurine = Anti-leukemia drug Acyclovir = Low oral absorption of 15-20% 8.115 = Toxic compound with a lower therapeutic index</p> Signup and view all the answers

    What enhances the oral absorption of acyclovir?

    <p>Using prodrugs</p> Signup and view all the answers

    Intracellular thiol levels are lower than in the blood for antimalarial compounds.

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

    What enzyme does 6-mercaptopurine inhibit in the purine nucleotide biosynthesis pathway?

    <p>several enzymes</p> Signup and view all the answers

    What is the primary mechanism of action for acyclovir?

    <p>Interference with viral DNA replication</p> Signup and view all the answers

    Acyclovir can be phosphorylated by uninfected cells.

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

    What does acyclovir resemble in structure?

    <p>2'-deoxyguanosine</p> Signup and view all the answers

    Acyclovir is a prodrug that must be activated by __________ before it can exert its effects.

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

    Which enzyme is NOT involved in the phosphorylation of acyclovir?

    <p>Viral phosphoglycerate kinase</p> Signup and view all the answers

    Match the following components with their roles in the activation and action of acyclovir:

    <p>Viral thymidine kinase = Activates acyclovir through phosphorylation Acyclovir triphosphate = Substrate for viral DNA polymerase Normal α-DNA polymerase = Not affected by acyclovir Incorporation into viral DNA = Leads to a dead-end complex</p> Signup and view all the answers

    Acyclovir triphosphate can effectively enter normal cells after being released.

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

    What is the outcome of incorporating acyclovir into viral DNA?

    <p>A dead-end complex is formed, disrupting viral replication.</p> Signup and view all the answers

    Study Notes

    N-Dealkylation

    • N-dealkylation is a metabolic reaction where an alkyl group is removed from a nitrogen atom
    • This reaction is often catalyzed by cytochrome P450 enzymes
    • An example of this reaction is the metabolism of alprazolam and triazolam
    • In these examples, the chlorine atom (X) can be either present or absent

    O-Dealkylation

    • O-dealkylation is a metabolic reaction where an alkyl group is removed from an oxygen atom
    • This reaction is often catalyzed by cytochrome P450 enzymes
    • An example is the metabolism of phenacetin to acetaminophen
    • Phenacetin is an analgesic, while acetaminophen is the active metabolite

    Oxidative Deamination

    • Oxidative deamination is a metabolic reaction where an amino group is removed from a molecule
    • This reaction is often catalyzed by cytochrome P450 enzymes
    • The reaction is important for the activation of certain drugs, including cyclophosphamide
    • Cyclophosphamide is an anti-cancer drug
    • It is activated by enzymes found in neoplastic (cancer) cells
    • Cyclophosphamide is converted into a reactive metabolite that can damage DNA

    Reductive Activation

    • Reductive activation is a metabolic reaction where a molecule is reduced
    • This reaction is often catalyzed by enzymes found in bacteria
    • An example is the metabolism of sulfasalazine
    • Sulfasalazine is used to treat inflammatory bowel disease
    • The drug is reduced to sulfapyridine, which is the active metabolite

    Disulfide Reduction

    • Disulfide reduction is a metabolic reaction where a disulfide bond is broken
    • This reaction can be catalyzed by enzymes or occur nonenzymatically.
    • An example is the metabolism of thiamine
    • Thiamine is poorly absorbed into the central nervous system (CNS)
    • Reduction of the disulfide bond in thiamine makes it more lipophilic, increasing absorption into the CNS

    Nucleotide Activation

    • Nucleotide activation is a metabolic reaction where a nucleotide is activated
    • This reaction is often catalyzed by enzymes
    • An example is the metabolism of 6-mercaptopurine
    • 6-mercaptopurine is an anti-leukemia drug
    • It is activated by enzymes that convert it to its active nucleotide metabolite
    • This metabolite inhibits enzymes involved in purine nucleotide biosynthesis

    Adenosine Deaminase

    • Adenosine deaminase is an enzyme that catalyzes the deamination of adenosine
    • Acyclovir is a drug that inhibits adenosine deaminase
    • Acyclovir has poor oral absorption, leading to the development of prodrugs
    • Prodrugs are designed to increase oral absorption

    Phosphorylation Activation

    • Phosphorylation activation is a metabolic reaction where a molecule is phosphorylated
    • This reaction is often catalyzed by enzymes
    • An example is the activation of acyclovir
    • Acyclovir is a drug that inhibits viral DNA polymerase
    • Acyclovir is selectively toxic to virus-infected cells due to phosphorylation by viral thymidine kinase
    • Sequential phosphorylations by viral enzymes convert acyclovir into its active triphosphate form
    • Acyclovir triphosphate inhibits viral DNA polymerase, but not normal DNA polymerase
    • Once incorporated into viral DNA, the triphosphate form of acyclovir creates a dead-end complex, preventing further replication
    • The acyclovir triphosphate is too polar to be taken up by normal cells
    • This selective toxicity allows acyclovir to target and destroy viruses without harming normal cells

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    Description

    Explore the fascinating metabolic reactions including N-dealkylation, O-dealkylation, and oxidative deamination, all catalyzed by cytochrome P450 enzymes. This quiz will test your understanding of these reactions and their significance in drug metabolism. Gain insights into the metabolism of substances like alprazolam, phenacetin, and cyclophosphamide.

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