Nucleotide Metabolism Flashcards
What is the rate limiting step of purine synthesis?
PRPP glutamyl amidotransferase
What is the rate limiting step of pyrimidine synthesis?
Carbamoyl phosphate synthetase II
What is the product of the N-10 formyl THF - dependent pathway?
Two molecules of N-10-formyl THF are required as one carbon donors in construction of the purine ring in purine nucleotide de novo synthesis.
Identify the enzyme that converts ribose-5-phosphate to its activated form, 5-phosphoribosyl-1-pyrophosphate.
PRPP synthetase
Which enzyme is inhibited by 5-fluorouracil?
Thymidylate synthase
True or False. Purine ring cannot be cleaved in human cells.
True, versus pyrimidine rings which can be opened and degraded to water soluble products.
What are the irreversible enzymes of the purine salvage pathway?
- Adenine phosphoribosyltransferase
- Hypoxanthine-guanine phosphoribosyltransferase
Lesch-Nyhan Syndrome is what enzyme deficiency?
HGPRT
Orotix Aciduria is characterized by what enzyme deficiency?
- Orotidine phosphate decarboxylase or
- Orotate phosphoribosyltransferase
What enzyme converts xanthine to uric acid?
Xanthine oxidase
The rate-limiting enzyme in this pathway wherein the initial reaction of the de novo synthesis for pyrimidine nucleotides begins with glutamine and CO2 and is complete with the formation of uridine monophosphate.
Aspartate Transcarbamoylase
How many of each base is found in complete double-stranded molecule:
A=20, G=25, C=30, and T=22
A= 42
G= 55
C= 55
T= 42
Cause of Hyperuricemia in a child who develops renal failure from Hyperuricemia on the second day of cytosine arabinoside therapy for acute myelogenous leukemia.
Increased catabolism of purines that are released from lysed leukemic cells
Which drug acts as a reversible inhibitor of IMP dehydrogenase, depriving T & B lymphocytes of nucleic acids?
Mycophenolate
Mechanism of action of doxorubicin in the treatment of lymphomas and breast cancers.
Inhibit Topoisomerase II
