Lecture 30: Nucleotide metabolism

Question 1

What is an important precursor for all nucleotides

Answer 1

PRPP

Question 2

Pyrimidines form nitrogenous bases ______ of PRPP

Answer 2

Independent

Question 3

What precursors are used for synthesis of pyrimidines

Answer 3

• NH3 from Glutamine
• Aspartate
• HCO3

Question 4

CAD

Answer 4

Multifunctional eukaryotic protein performs functions of
Carbamoyl phosphate synthetase II
Aspartate transcarbamoylase
Dihydroorotase

Question 5

Carbamoyl phosphate synthetase

Answer 5

Synthesizes carbamoyl phosphate from bicarbonate

Question 6

Aspartate transcarbamoylase allosteric regulators

Answer 6

ATP activates

CTP inhibits

Question 7

Dihydroorotase function

Answer 7

Closes the ring, acts as a hydrolase in reverse

Question 8

UMP synthetase

Answer 8

Removes PPi when orotate added to PRPP

Decarboxylates orotate to form uracil

Question 9

Nucleotide monophosphate kinases

Answer 9

Create diphosphates from monophosphates
They are specific to each nucleotide monophosphate
i.e. UMP has its own, AMP has its own

Question 10

Nucleotide diphosphate kinase

Answer 10

Broad specificity, creates triphosphates from diphosphates

Question 11

What is the only nucleotide to be synthesized directly as a triphosphate

Answer 11

CTP

Question 12

CTP synthetase allosteric regulators

Answer 12

GTP activates

CTP inhibits

Question 13

Purines and PRPP

Answer 13

Purines form nitrogenous base on PRPP

Question 14

Precursors for purines

Answer 14

• NH3 from glutamine
• Glycine
• Asparatate
• N10-Formyl-THF
• HCO3

Question 15

Regulation of synthesis of purines

Answer 15

Feedback inhibition by purines

Question 16

Which molecule is formed in purine synthesis that has the option to either go down the Adenine or Guanine synthesis pathways

Answer 16

Ionosine monophosphate

Question 17

What is used for energy when making AMP (adenine monophosphate)

Answer 17

GTP

Question 18

What replaces the carbonyl group in IMP when forming AMP- and what is released

Answer 18

NH3 from aspartate

Fumarate is released

Question 19

What inhibits formation of AMP

Answer 19

AMP

Question 20

What is used for energy when making GMP

Answer 20

ATP

Question 21

How is tertiary NH3 grouped formed when making GMP from IMP

Answer 21

Redox with H20 to make second carbonyl, then that carbonyl is replaced with NH3 from Glutamine

Question 22

What inhibits formation of GMP

Answer 22

GMP

Question 23

What provides necessary electrons for redox reactions in deoxyribonucleotide synthesis

Answer 23

NADPH

Question 24

Ribonucleotide reductase is activated/inhibited by

Answer 24

ATP activates

dATP inhibits

Question 25

If dATP occupies the allosteric specificity site of ribonucleotide reductase, what is preferred in the active site

Answer 25

Pyrimidines

Question 26

If dTTP is in the allosteric specificity site of RR, what is preferred in the active site

Answer 26

GDP preferred | Pyrimidines inhibited

Question 27

If dGTP is in the allosteric specificity site of RR, what is preferred in the active site

Answer 27

ADP preferred | Pyrimidines inhibited

Question 28

What are the two ways to create dUMP

Answer 28

Removal of PPi from dUTP | Deamination of dCMP

Question 29

Function of Thymidylate synthase

Answer 29

Adds a methyl group to dUMP to create dTMP

Question 30

Difference between endo and exonucleases

Answer 30

Endonucleases cut in the middle | Exonucleases chew from the end

Question 31

In salvage of pyrimidines, there are two types enzymes that create two products. What are the enzymes and their products

Answer 31

Phosphorylases make nucleosides | Kinases make nucleotides

Question 32

How many steps are involved in salvage of pyrimidines and how many for purines

Answer 32

2 steps for pyrimidine salvage | 1 step for purine salvage

Question 33

What enzyme is used for salvage of purines

Answer 33

Phosphoribosyltransferases

Question 34

What is the final product of purine catabolism

Answer 34

Uric acid

Question 35

What is the enzyme that catalyzes the final step in the breakdown of pyrimidines

Answer 35

Ureidopropionase

Question 36

What enzyme makes AMP during salvage of purines

Answer 36

Adenine phosphoribosyltransferase

Question 37

What enzyme makes IMP/GMP during salvage of purines

Answer 37

Hypoxanthine-Guanine phosphoribosyltransferase

Question 38

What are required to make GMP

Answer 38

Glutamine | ATP

Question 39

What are required to make AMP

Answer 39

Aspartate | GTP

Question 40

What are required to make IMP

Answer 40

Glycine Glutamine N10-Formyl-THF HCO3