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MCM > Nucleotide Metabolism > Flashcards

Nucleotide Metabolism Flashcards

1
Q

What molecules are purines?

A

Adenosine, and Guanine

Pur As Gold

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2
Q

what reaction does UMP synthase catalyze?

A

Orate –> UMP

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3
Q

What vitamin does methotrexate compete w/?

A

folate (B9)

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4
Q

what does uridine phosphorylase do?

A

catalyzes Uracil –> uridine

in pyrimidine salvage

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5
Q

What is the rate limiting step and enzyme in purine synthesis?

A

PRPP —->PRA

through GPPA

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6
Q

What is the very basic sequence of purine synthesis?

A

Sugar made, add base

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7
Q

What is the rate limiting reaction and enzyme in pyrimidine synthesis?

A

Carbamoyl phosphate –> carbamoyl aspartate

enzyme: aspartate transcarbamoylase

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8
Q

What molecules are pyrimidines?

A

Cytosine, Uracil, Thymine

CUT the Py

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9
Q

What is the very basic sequence of pyrimidine synthesis?

A

Make base first, then add sugar

think this because the base is 1 ring, simple, so it’s made first

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10
Q

What is the basic path of uracil salvage (pyrimidine)?

A

Uracil –uridine phosphorylase–> uridine –>–>–> UTP

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11
Q

What is gout?

A

overproduction of uric acid usually because of diet high in purines/red meat; sodium urate turns into crystals that are painful and accumulate in toes and fingers (high concentration, low temp)
note: NO defect in anything

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12
Q

What is acyclovir and how does it work?

A

antiviral used to treat herpes and chicken pox

acts like a nucleoside in DNA formation and binds with phosphate –> blocks thymidine kinase and inhibits DNA formation

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13
Q

What is the sequence of molecules in purine synthesis?

A

RiPPIA

Ribose-5-P –> PRPP –> PRA –> IMP –> AMP and GMP

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14
Q

what does thymine kinase do? What is it inhibited by?

A

catalyzes deoxythyuridine to dTTP in pyrimidine salvage

inhibitted by acyclovir

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15
Q

What enzyme is essential in GMP and IMP (purine) salvage? What is its co-enzyme?

A

Hypoxanthine-guanine phosphoribosyl transferase
(HGPT)
Guanine or Hypoxanthine –HGPT–>GMP/IMP
PRPP is the co-enzyme

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16
Q

What does adenosine deaminase do and what is its clinical relevance?

A

adenosine –> inosine (in Purine salvage)
when in excess –> hemolytic anemia
when deficient –> SCID

17
Q

what does the enzyme CPS II do?

A

gln –> carbamoyl phosphate in pyrimidine synthesis

18
Q

What is 5-fluorouracil and what does it do?

A

Cancer drug more potent than methotrexate

blocks thymidylate synthase, which gets UMP to thymine derivatives in pyrimidine synthesis and stops production of DNA

19
Q

How is gout treated? What increases when it is treated?

A

allopurinol inhibits xanthine oxidase (hypoxanthine –> xanthine –>uric acid)
hypoxanthine and xanthine increase, but are more water soluble that uric acid so don’t cause symptoms

20
Q

What enzyme is essential in AMP (purine) salvage?

A

Adenine phophoribosyltransferase
(APRT)
A –APRT–>AMP

21
Q

What does methotrexate do?

A

cancer drug that inhibits PRA –>IMP in purine synthesis

by acting as a competitive inhibitor with folate

22
Q

How do sulfa drugs work?

A

Inhibit PABA –> folate in bacteria only

23
Q

What is the basic path of thymine salvage?

A

thymine –> deoxythuridine –>–>dTTP

24
Q

What does PRPP synthetase do?

A

Ribose-5-P to PRPP in purine synthesis

25
Q

What is the sequence of Purine (AMP) degradation?

A

AMP –> adenosine –> Inosine –> hypoxanthine –> xanthine –> uric acid

26
Q

What disease is associated with a decreased function in HGPRT? What are some symptoms?

A

Lesch-Nyhan syndrome. Inhibits purine salvage. Symptoms: increased uric acid, poor muscle control mental retardation, tendency to self-mutilate

27
Q

What are the steps of pyrimidine synthesis?

A

GCCDOUT
glutamine –> carbamoyl phosphate –> carbamoyl aspartate –> dehydroorate –> orate –> UMP –> thymine and cytosine derivatives

28
Q

What is orotic aciduria and how is it treated?

A

defect in UMP synthases, treated with oral uridine

MCM (14 decks)

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