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Biochemistry > Lecture 30: Nucleotide metabolism > Flashcards

Lecture 30: Nucleotide metabolism Flashcards

1
Q

What is an important precursor for all nucleotides

A

PRPP

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2
Q

Pyrimidines form nitrogenous bases ______ of PRPP

A

Independent

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3
Q

What precursors are used for synthesis of pyrimidines

A
  • NH3 from Glutamine
  • Aspartate
  • HCO3
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4
Q

CAD

A

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

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5
Q

Carbamoyl phosphate synthetase

A

Synthesizes carbamoyl phosphate from bicarbonate

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6
Q

Aspartate transcarbamoylase allosteric regulators

A

ATP activates

CTP inhibits

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7
Q

Dihydroorotase function

A

Closes the ring, acts as a hydrolase in reverse

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8
Q

UMP synthetase

A

Removes PPi when orotate added to PRPP

Decarboxylates orotate to form uracil

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9
Q

Nucleotide monophosphate kinases

A

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

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10
Q

Nucleotide diphosphate kinase

A

Broad specificity, creates triphosphates from diphosphates

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11
Q

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

A

CTP

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12
Q

CTP synthetase allosteric regulators

A

GTP activates

CTP inhibits

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13
Q

Purines and PRPP

A

Purines form nitrogenous base on PRPP

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14
Q

Precursors for purines

A
  • NH3 from glutamine
  • Glycine
  • Asparatate
  • N10-Formyl-THF
  • HCO3
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15
Q

Regulation of synthesis of purines

A

Feedback inhibition by purines

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16
Q

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

A

Ionosine monophosphate

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17
Q

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

A

GTP

18
Q

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

A

NH3 from aspartate

Fumarate is released

19
Q

What inhibits formation of AMP

A

AMP

20
Q

What is used for energy when making GMP

A

ATP

21
Q

How is tertiary NH3 grouped formed when making GMP from IMP

A

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

22
Q

What inhibits formation of GMP

A

GMP

23
Q

What provides necessary electrons for redox reactions in deoxyribonucleotide synthesis

A

NADPH

24
Q

Ribonucleotide reductase is activated/inhibited by

A

ATP activates

dATP inhibits

25
Q

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

A

Pyrimidines

26
Q

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

A

GDP preferred

Pyrimidines inhibited

27
Q

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

A

ADP preferred

Pyrimidines inhibited

28
Q

What are the two ways to create dUMP

A

Removal of PPi from dUTP

Deamination of dCMP

29
Q

Function of Thymidylate synthase

A

Adds a methyl group to dUMP to create dTMP

30
Q

Difference between endo and exonucleases

A

Endonucleases cut in the middle

Exonucleases chew from the end

31
Q

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

A

Phosphorylases make nucleosides

Kinases make nucleotides

32
Q

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

A

2 steps for pyrimidine salvage

1 step for purine salvage

33
Q

What enzyme is used for salvage of purines

A

Phosphoribosyltransferases

34
Q

What is the final product of purine catabolism

A

Uric acid

35
Q

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

A

Ureidopropionase

36
Q

What enzyme makes AMP during salvage of purines

A

Adenine phosphoribosyltransferase

37
Q

What enzyme makes IMP/GMP during salvage of purines

A

Hypoxanthine-Guanine phosphoribosyltransferase

38
Q

What are required to make GMP

A

Glutamine

ATP

39
Q

What are required to make AMP

A

Aspartate

GTP

40
Q

What are required to make IMP

A

Glycine
Glutamine
N10-Formyl-THF
HCO3

Biochemistry (20 decks)

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