Exam 18: Nucleotide Metabolism

A mutation in __________ may alter the rate at which UT is converted to CTP.

In analyzing the intermediates formed during the conversion of IMP to GMP and AMP,which molecule would one expect to find in the conversion to GMP but NOT in the conversion to AMP?

What would be the effect on the enzyme activity of a mutant ribonucleotide reductases in which the metal-coordinated Tyr is missing? Explain your reasoning in the context of the role of the Tyr in the mechanism of the enzyme.

An E.coli strain that is unable to synthesize purines because of a mutation in the gene encoding the AIR synthetase is transfected with the human gene coding for hTrifGART.Would this strain would be able to undergo mitosis in purine-depleted media? Explain your answer.

Mutations in HGPRT cause Lesch-Nyhan syndrome.Mutations can lead to two different outcomes,both of which result in a reduction of guanine salvaging in cells.Contrast the two classes of mutations in HGPRT that can lead to the same result.

How many of the nitrogens in orotidine- -monophosphate arise from glutamine?

Identify the carbon atom that is attacked by Cys439 in the first step of the E.coli ribonucleotide reductase mechanism.

Complete the following pathway of the degradation of UMP. UMP Uridine __________ Dihydrouracil __________ NH₄₊ + HCO₃- + -alanine

Which enzyme activity would be directly reduced if fluorodeoxyuridine- -monophosphate is present?

To study the allosteric regulation of E.coli ribonucleotide reductase in a cell-free in vitro system,which of the following would be a good choice to add to the system?

Contrast the energy required to drive the synthesis of AMP from IMP with that required to drive the synthesis of GMP from IMP.

Purine biosynthesis takes place in two stages.The first stage begins with ribose-5-phosphate and ends with

Which enzyme activity would be directly inhibited by the addition of methotrexate?

To purify glutathione reductase to carry out a kinetics analysis,which organism would be the best source of the enzyme?

Which of the following organisms would generate this compound?

The molecule below is a precursor to the formation of which of the following second messengers?

What is the name of the compound below,which is part of the pathway that regenerates N⁵,N¹⁰-methylenetetrahydrofolate?

A person wishes to determine the role of PRPP synthetase in a newly discovered organism.He or she decides that a good way to do this would be to see what happens when PRPP synthetase is inhibited.Which of the following could be added to a cell from this organism to inhibit PRPP synthetase?

Dihydropyrimidine dehydrogenase deficiencies can lead to an intolerance of high doses of 5-fluorouracil because 5-fluorouracil __________ dihydropyrimidine dehydrogenase.

The biosynthesis of deoxynucleosides is important,yet different organisms require different sets of enzymes to carry it out.If 100 different species were analyzed,which enzyme is most likely to be found in all of them?