Nucleotide Metabolism Exam 1 BioC

What are the 2 ways that nucleotides can be synthesized?

De novo or by salvage pathways

If nucleotides are synthesized de novo then they are derived from?

simple precursors such as amino acids

If nucleotides are synthesized via salvage pathways they are derived from?

recovered nitrogenous bases attached to an activated ribose (PRPP)

What does PRPP stand for?

phosphoribosyl pyrophosphate

What are the 3 precursors of the pyrimidine ring?

bicarbonate, NH3 and aspartate

What are the precursors of the purine ring?

glycine, glutamine, aspartate, CO2 and tetrahydrofolate

What molecule are purines synthesized on in the de novo pathway?

A. phosphate

B. deoxyribose

C. ribose

D. ribonucleotide

C. ribose

If UTP is methylated it turns into what?

TTP

If UTP gets aminated it turns into what?

CTP

What is the product of 5-phosphoriobsyl-1-amine after nine steps in the de novo purine biosynthesis?

IMP (inosinate)

IMP can be converted into ____ and ____ for RNA and then turned into ____ and ____ for DNA

ATP and GTP; dATP and dGTP

In the de novo pathway purines are synthesized on a ____ molecule

ribose

What enzyme catalyzes the reaction of PRPP and glutamine into 5-phsophoribosyl-1amine?

glutamine phosphoribosyl amidotransferase

What is the leaving group when 5-phosphoribosyl-1-amine forms from PRPP and glutamine?

PPi (pyrophosphate)

How many steps does it take to convert 5-phosphoribosyl-1-amine into IMP (inosine monophosphate)?

9

IMP is converted into ____ and ____

AMP and GMP

IMP is converted into adenylate (AMP) in a pathway that requires:

A. GMP

B. GTP

C.AMP

D.ATP

B. GTP

IMP is also metabolized to guanosine monophosphate (GMP or guanylate) in a pathway that requires:

A. GMP

B. GTP

C.AMP

D.ATP

D.ATP

What amino acid is used to convert IMP to AMP?

A. D

B. G

C. E

D. Q

E. A

A. D ... Asp Aspartate

What amino acid is used to convert IMP to GMP?

A. D

B. G

C. E

D. Q

E. A

D. Q Gln Glutamine

What are the 2 salvage enzymes that recycle purine bases?

APRT (adenine phosphoribosyl transferase) and HGPRT (hypoxanthine-guanine phosphoribosyl transferase)

In the regulation of purine biosynthesis what 3 end products inhibit the enzyme glutamine-PRPP amidotransferase?

IMP, AMP and GMP

What does excess GMP inhibit?

It inhibits IMP dehydrogenase which inhibits the formation of xanthylate

What is PRPP synthesis inhibited by?

ADP and GDP

What is formed in the first step in the pyrimidine synthesis that consists of a 3-step reaction?

carbamoyl phosphate

What enzyme catalyzes bicarbonate to carbamoyl phosphate?

carbamoyl phosphate synthetase II (CPS II)

Carbamoyl phosphate reacts with aspartate to form carbamoylaspartate and is catalyzed by what enzyme?

A. carbamoyl phosphate synthetase II

B. PRPP synthetase

C. aspartate transcarbamolyase (ATCase)

D. carbamoyl synthetase

C. aspartate transcarbamolyase (ATCase)

What is the key regulatory enzyme in pyrimidine synthesis?

A. PRPP synthetase

B. aspartate transcarbamolyase (ATCase)

C. glutamine-PRPP amidotransferase

D. Ribonucleotide reductase

B. aspartate transcarbamolyase (ATCase)

Carbamoylasparate is metabolized to what?

orotate

What is the intermediate molecule of carbamoylasparate and orotate?

dihydroorotate

Orotate reacts with PRPP to form what?

orotidylate

What is the leaving group when orotate reacts with PRPP to form OMP (orotidylate)?

PPi

Orotidylate is converted to uridylate (OMP to UMP) by what enzyme?

orotidylate decarboxylase

UMP is converted to UDP and UTP via what type of enzyme?

kinases because they add phosphates

What type of enzymes remove phosphates?

phosphatases

What enzyme catalyzes UTP to CTP?

Cytidylate synthetase

Rising levels of CTP inhibits what enzyme?

A. carbamoyl phosphate synthetase II

B. cytidylate synthetase

C. ACTase

D. PRPP synthetase

C. ACTase

What amino acid provides the amino group for the replacement of the carbonyl group with an amino group of UTP to CTP?

A. D

B. E

C. Q

D. N

E. R

C. Q, Gln Glutamine

What enzyme incorporates the salvaged thymine into a nucleoside thymidine?

thymidine phosphorylase

What enzyme generates the nucleotide of thymidine?

thymidine kinase

Ribonucleotides are precursors to deoxynucleotides how?

The 2' carbon of the sugar is reduced from OH to H (ribose to deoxyribose)

What enzyme catalyzes the reduction of ADP to dADP?

ribonucleotide reductase converts ribonucleotides to deoxynucleotides (NDP -> dNDP)

Oxidation is the addition of _____ atom, the loss of _____ and the removal of ___.

Oxygen; electrons; H+

Reduction is the removal of _____ atom, the addition of _____ and the gain of _____

Oxygen; H+; electrons

What is the amino acid attached to ribonucleotide reductase that become oxidized when the reduction ribonucleotides to deoxynucleotides takes place?

cysteine (thiol) -SH oxidized to S-S

What is the enzyme that catalyzes dCTP to dUTP?

A. ribonucleotide reductase

B. deaminase

C. thymidylate synthase

D. cytidylate synthetase

B. deaminase

What is the enzyme that catalyzes dCDP to dCTP and dUDP to dUTP?

A. nucleoside diphosphate kinase

B. ribonucleotide reductase

C. thymidylate synthase

D. PRPP synthase

A. nucleoside diphosphate kinase

What enzyme catalyzes dUTP to dUMP?

A. PRPP synthase

B. orotidylate decarboxylase

C. dUTPase

D. nucleoside diphosphate kinase

c. dUTPase

What enzyme catalyzes dUMP to dTMP?

A. dUTPase

B. thymidine kinase

C. thymidine phosphorylase

D. thymidylate synthase

D. thymidylate synthase

What is the enzyme that catalyzes tetrahydrofolate to N5, N10 -methylenetetrahydrofolate?

A. dihydrofolate reductase

B. tetrahydrofolate reductase

C. serine hydroxymethyl-transferase

D. thymidylate synthase

C. serine hydroxymethyl-transferase

What is the enzyme that catalyzes 7,8-dihydrofolate to tetrahydrofolate?

A. dihydrofolate reductase

B. tetrahydrofolate reductase

C. serine hydroxymethyl-transferase

D. thymidylate synthase

A. dihydrofolate reductase

Thymidylate is formed by the ____ of deoxyuridylate.

methylation

What enzyme catalyzes the reaction of IMP to adenylosuccinate?

A. adenylosuccinate ligase

B. adenylosuccinate lyase

C. adenylosuccinate synthetase

D. adenylosuccinate transferase

C. adenylosuccinate synthetase

Whay enzyme catalyzes the reaction of adenylosuccinate to adenylate?

A. adenylosuccinate synthetase

B. adenylosuccinate ligase

C. adenylosuccinate transferase

D. adenylosuccinate lyase

D. adenylosuccinate lyase

What enzyme catalyzes inosinate to xanthylate?

A. IMP transferase

B. IMP dehydrogenase

C. XMP-glutamine amidotransferase

D. XMP dehydrogenase

B. IMP dehydrogenase

What enzyme catalyzes xanthylate to guanylate?

A. GMP transferase

B. GMP dehydrogenase

C. XMP-glutamine amidotransferase

D. XMP dehydrogenase

C. XMP-glutamine amidotransferase

Write out of the name of CTP.

cytidine-5-triphosphate

Write out the name of GDP.

guanosine-5-diphosphate

Write out the name of ATP.

adenosine-5-triphosphate

What is the name of TMP also known as dTMP?

thymidylate or deoxythymidylate

What is the name of dAMP?

deoxyadenylate

What is the name of dCDP?

deoxycytidine-5-diphosphate

What is the name of CMP?

cytidylate or cytidine-5-monophosphate

What is A base name?

adenine

What is T base name?

thymine

What is C base name?

cytosine

Which base is strictly RNA?

Uracil (U)

Name the 4 ribonucleosides.

adenosine, guanosine, uridine, cytidine

Name the 5 nucleotides.

adenylate, guanylate, uridylate, cytidylate, thymidylate

What enzyme dephosphorylates guanylate to guanosine?

5'-nucleotidase (Mono ribonucleotide to nucleoside) (GMP to guanosine)

What enzyme dephosphorylates adenylate to adenosine?

5'-nucleotidase (Mono ribonucleotide to nucleoside) (AMP to adenosine)

Which enzyme catalyzes adenosine to inosine?

A. nucleosidase

B. adenosine deaminase

C. inosine deaminase

D. nucleotidase

B. adenine deaminase

What enzyme catalyzes inosine to hypoxanthine?

A. nucleosidase

B. adenosine deaminase

C. inosine deaminase

D. nucleotidase

A. nucleosidase

What enzyme catalyzes hypoxanthine to xanthine?

A. xanthine reductase

B. xanthine deaminase

C. xanthine oxidase

D. xanthine nucleotidase

C. Xanthine oxidase

What enzyme catalyzes guanine to xanthine?

A. guanine deaminase

B. guanine oxidase

C. guanine reductase

D. guanine nucleotidase

A. guanine deaminase

What enzyme catalyzes xanthine to uric acid?

A. xanthine reductase

B. uric acid reductase

C. xanthine oxidase

D. uric acid oxidase

C. xanthine oxidase

Which enzymes are used to in the production of uric acid from GMP? Select all the apply:

A. xanthine reductase

B. xanthine oxidase

C. guanine deaminase

D. nucleosidase

E. xanthine synthetase

B, C, D

Which statement is true of the biosynthetic pathway for purine nucleotides?

A. Inosinate is the purine nucleotide that is the precursor of both adenylate and guanylate.

B. Deoxyribonucleotides are formed from 5-phosphodeoxyribosyl 1-pyrophosphate.

C. The amino acid valine is one of the precursors contributing to purine nucleotides.

D. Orotidylate is an essential precursor for purine nucleotides.

E. CO2 does not participate in any of the steps in this pathway

A.

In purine biosynthesis, which contributes two of the ring nitrogen's?

A. aspartate

B. urea

C. glycine

D. asparagine

E. glutamine

E. glutamine

Precursors for the biosynthesis of the pyrimidine ring system include:

A. glycine and succinyl-CoA.

B. carbamoyl phosphate and aspartate.

C. glutamate, NH3, and CO2.

D. glutamine and aspartate.

E. glycine, glutamine, CO2, aspartate and tetrahydrofolate

B. carbamoyl phosphate and aspartate

The ribosyl phosphate moiety needed for the synthesis of orotidylate, inosinate, and guanylate is provided by:

A. guanosine 5'-phosphate.

B. cytosine 5'-phosphate.

C. ribulose 5-phosphate.

D. 5-phosphoribosyl-1-pyrophosphate.

E. ribose 5-phosphate.

D. PRPP

5-Fluorouracil is used for the treatment of cancer. It inhibits this enzyme

A. dihydrofolate reductase

B. thymidylate synthase

C. thymidylate phosphorylase

D. thymidylate kinase

B. thmidylate synthase

Glutamine is a nitrogen donor in the synthesis of:

A. inosinate.

B. dTTP.

C. UMP.

D. CTP.

E. orotate.

A. inosinate (IMP)

Which is the immediate precursor of thymidylate (dTMP)?

A. dUMP

B. dCTP

C. dGMP

D. dATP

E. UTP

A. dUMP

Which is the product of purine degradation in humans?

A. uric acid

B. succinate

C. urea

D. glutamate

E. NH4+

A. Uric acid

What is the direct precursor of uric acid in the catabolism of purines?

A. hypoxanthine

B. inosine

C. xanthine

E. xanthosine

C. xanthine

What is the enzyme that catalyzes the first step in thymine breakdown to dihydrothymine?

A. thymine dehydrogenase

B. dihydrothymine dehydrogenase

C. dihydrouracil dehydrogenase

D. uracil dehydrogenase

C. dihydrouracil dehydrogenase

What is the cofactor that is oxidized when dihydrouracil dehydrogenase reduces thymine to dihydrothymine?

A. NADH

B. NAD+

C. NADPH + H+

D. NADP+

E. FADH

C. NADPH + H+

Painful joints due to deposits of sodium urate crystals often in extremities like the toes is known as ______

Gout

The drug known as _____ is used to treat gout to prevent the formation of uric acid.

Allopurinol

What enzyme does Allopurinol inhibit?

A. hypoxanthine oxidase

B. xanthine reductase

C. hypoxanthine reductase

D. xanthine oxidase

D.

What human organ is especially dependent on salvage pathways?

The brain

What enzymes do the drugs azaserine and acivicin inhibit?

A. thymidylate synthase

B. dihydrofolate reductase

C. glutamine amidotransferases

D. cytidylate synthetase

C. glutamine amidotransferases

What drugs inhibit dihydrofolate reductase? Select all that apply:

A. Methotrexate

B. azaserine

C. aminopterin

D. acivicin

E. trimethoprim

A,C,E

What drug is converted into a molecule by the salvage pathway to inhibit thymidylate synthase?

A. Fluoroquinolones

B. Fluorouracil

C. Fluorine

D. Trimethoprim

B. Fluorouracil