LECTURE 26 - METABOLISM OF NUCLEOTIDES Flashcards
Name the nucleobase of Cytidine
Cytosine
Name the nucleobase of Hypoxanthine
Inosine
Name the nucleobase of adenosine
adenine
Identify the commitment step for the de novo synthesis of purine and pyrimidine bases
The first step is the commitment step; highly regulated
PRPP → 5-phosphoribosylamine
Identify the key starting material for the de novo synthesis of purine and pyrimidine bases
PRPP (5-phosphoribosyl-1-pyrophosphate)
List the allosteric regulators of purine synthesis
AMP
GMP
IMP
Distinguish the salvage pathway from the de novo synthesis of nucleotides
de novo synthesis builds nucleotides from scratch (amino acids)
The salvage pathway reuses partially broken down nucleotide components
Identify the end product of the degradation of purine nucleobases
uric acid
Explain the mechanism of allopurinol in gout prevention
Inhibits xanthine oxidase, which is an enzyme that catalyzes a reaction that forms uric acid
(Reduces the production of uric acid)
Increases the utilization of hypoxanthine through the salvage pathway, which reduces de novo purine synthesis
Explain the activation mechanisms of nucleobase analog drugs
Phosphorylation to their triphosphate form
Explain the antiviral mechanism of acyclovir
- Antiviral drug used to treat herpes simplex virus (HSV) infections
- Converted to the monophosphate by a HSV-thymidine kinase, which exists only in the infected cells
- The triphosphate is used as a substrate for the HSV DNA polymerase, causing chain termination
Explain the antiviral mechanism of sofosbuvir
- Antiviral drug used to treat hepatitis C
- Is a prodrug → converted to active agent in vivo
- The active agent is a potent inhibitor of NS5B, which is a RNA-dependent RNA polymerase
