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Biochem test 3 > Lecture 30 - Nucleotide Formation > Flashcards

Lecture 30 - Nucleotide Formation Flashcards

1
Q

What is PRPP and where does it come from?

L30 S5

A

5-phospho-α-D-ribosyl-1-pyrophosphate

Derived from ribose-5-phosphate (pentose phosphate pathway) and can be used in synthesis of all neucleotides

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2
Q

What are the characteristics of pyrimidine synthesis (PRPP dependency, branched/linear, location, and precursors)?

L30 S6

A

PRPP independent

Linear pathway

Occurs in cytoplasm

Precursors:

  • Gln
  • Asp
  • HCO3
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3
Q

What are the characteristics of purine synthesis (PRPP dependency, branched/linear, location, and precursors)?

L30 S15

A

PRPP dependent (base synthesized on PRPP)

Branched pathway (inosine is made first and then either GMP or AMP)

Occurs in cytoplasm

Precursors:

  • Gln (NH3)
  • Aspartate and glycine
  • N10-formal-THF
  • HCO3
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4
Q

How is UMP synthesized and what regulates it?

L30 S7

A

Formed from HCO3-, glutamine (NH3), and aspartate

Base is formed without PRPP

Promoters:
-ATP (ATP pairs with UMP, dTTP comes from UMP, so if there is excess ATP more UMP is needed)

Inhibitors:
-CTP (CTP is made from UMP so if there is excess CTP, more UMP is not needed)

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5
Q

How is CTP synthesized and what regulates it?

L30 S7

A

CTP is made from UTP (unidirectional pathway)

Base is formed without PRPP

Promoters:
-GTP (cytosine pairs with guanine so if there is excess GTP, more CTP is needed)

Inhibitors:
-CTP (inhibits excessive production of itself)

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6
Q

How is GMP synthesized and what regulates it?

L30 S25

A

Synthesized from IMP (branched pathway)

Additional NH3 is from glutamine (bond energy from GTP) at secondary carbonyl which is from water

IMP synthesized with PRPP

Inhibitors:
-GTP (inhibits excessive production of itself)

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7
Q

How is AMP synthesized and what regulates it?

L30 S25

A

Synthesized from IMP (branched pathway)

Carbonyl replaced by NH3 which is from aspartate (bond energy from ATP)

IMP synthesized with PRPP

Inhibitors:
-ATP (inhibits excessive production of itself)

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8
Q

What is ATCase and what is significant about it?

L30 10

A

Aspartate transcarbamoylase

Regulatory enzyme of pyrimidine synthesis (carbonyl + aspartate -> carbamoyl aspartate)

Promoted by:
-ATP

Inhibited by:
-CTP

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9
Q

What is dihydroortate dehydrogenase and what is significant about it?

L30 S11

A

Enzyme of pyrimidine synthesis (dihydroorotate -> orotate)

Found in the mitochondria and uses FMN producing FMNH2 which is passed to Q of the ETC

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10
Q

What is dihydroorotase and what is significant about it?

L30 S11

A

Enzyme of pyrimidine synthesis (carbamoylaspartate -> dihydroorotate + H20)

Closes ring

Opposite of a hydrolase (she really like this

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11
Q

What is CTP synthetase and what is significant about it?

L30 S15

A

Regulatory enzyme of pyrimidine synthesis (UTP -> CTP)

Promoted by:
-GTP

Inhibited by:
-CTP

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12
Q

What is UMP synthase and what is significant about it?

L30 S12

A

Enzyme of pyrimidine synthesis (add PRPP to orotate and converts orotate to uracil)

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13
Q

What are nucleotide monophosphate kinases and what is significant about them?

L30 S14

A

Phosphorylates monophosphates to diphosphates

Unique to each NMP

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14
Q

What are nucleotide diphosphate kinases and what is significant about them?

L30 S14

A

Phosphorylates diphosphates to triphosphates

Not specific for certain NDP

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15
Q

What is the purinosome and what is significant about it?

L30 S23

A

Enzyme of purine synthesis.

Consists of 6 enzymes that perform the 10 reactions of purine synthesis

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16
Q

What is rNDP reductase and what is significant about it?

L30 S28

A

Converts NDPs to dNDPs (or NTPs to dNTPs)

17
Q

What is special about dTTP synthesis?

L30 S27

A

Must go through dUMP from dUDP or dCDP first

18
Q

Differentiate between endonucleases and exonucleases.

L30 S39

A

Endonuclease:
-cuts in the middle

Exonuclease:
-cuts from the ends

19
Q

What results from HPRT deficiency?

L30 S48

A

Leach-Nyhan syndrome

20
Q

What results from adenosine deaminase deficiency?

L30 S49

A

SCID

21
Q

What results from UMP synthetase deficiency?

L30 S13

A

Megaloblastic anemia

22
Q

What is the significance of acyclovir?

L30 S42

A

Is accepted by viral thymidine kinase and acyclovir triphosphate acts as a terminator of DNA synthesis if incorporated into DNA

Biochem test 3 (11 decks)

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