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Flashcards in Nucleotide Metabolism Deck (12):

What are the biosynthesis intermediates of IMP?

Adenylosuccinate and Xanthosine (Xanthylate). These are further converted into ATP and GTP respectively.


What is the committed step in Purine synthesis?

the formation of Phosphoribosylamine (PRA) from PRPP.


Methotrexate: Function

It is an anticancer agent. It prevents oxidation of NADPH by DHFR.
It is a competitive inhibitor of many enzymes that utilize Folate. It has a higher affinity. It disrupts DNA replication in rapidly replicating cells.


What are Sulfa Drugs and what is their function?

Competitive inhibitors of the bacterial enzyme that incorporates PABA into folate.
Disrupts DNA replication selectively in bacteria.


What inhibits Carbamoyl Phosphate Synthetase II?
What stimulates it?

UMP and Purines.
PRPP stimulates it.


What is the rate limiting enzyme in Pyrimidines synthesis?
What inhibits it?

Aspartate Transcarbamoylase. It converts Carbamoyl Phosphate into Carbamoyl Aspartate.
Inhibited by CTP.


What is 5-Fluorouracil?

Anticancer agent in Pyrimidines synthesis. Most likely inhibits the Thymidylate Synthase.


What causes Orotic Aciduria?
How is it treated?

effective enzyme in the process of PRPP+orotate=UMP.
It is treated with oral Uridine.


Excessive Adenosine Deaminase causes what condition?
What is the function of this enzyme?

Hemolytic Anemia
Converts Adenosine to Inosine during the Purine degradation process. Triggers destruction of RBCs.


What is the function of Allopurinol?

Inhibits the xanthine oxidase enzyme (this enzyme is responsible of conversion of Hypoxanthine to Xanthine and the conversion of Xanthine to Uric Acid.) The accumulation of uric acid causes Gout; therefore this is a treatment of Gout.


Underproduction of Adenosine Deaminase cause what condition?

Severe Combined Immunodeficiency (SCID).


Lesch-Nyhan Syndrome

caused by a deficiency in the HGPRT enzyme in the purine salvage pathway. This enzyme converts Guanine and Hypoxanthine to GMP or IMP. This leads to overproduction of Uric Acid.