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Biochemistry > Purine Metabolism > Flashcards

Purine Metabolism Flashcards

1
Q

What are the two subtypes of nucleotides?

A

Pyrimidines and purines

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2
Q

How many rings do purines have in their nitrogenous base?

A

Two rings

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3
Q

What is the major cellular source of energy?

A

ATP (adenosine triphosphate)

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4
Q

What does cyclic AMP stand for?

A

Cyclic adenosine monophosphate

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5
Q

True or False: Cyclic GMP serves as a second messenger.

A

True

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6
Q

What are exogenous nucleotides?

A

Nucleotides obtained from the diet

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7
Q

What are endogenous nucleotides?

A

Nucleotides synthesized by the body

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8
Q

What is the first step in purine synthesis?

A

Creation of PRPP (5 phosphoribosyl 1 pyrophosphate)

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9
Q

What does IMP stand for?

A

Inosine Monophosphate

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10
Q

What are the basic components of nucleotides?

A

Phosphate group, ribose sugar, base

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11
Q

What is the role of folate in purine synthesis?

A

Contributes single carbon groups

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12
Q

List the amino acids that provide nitrogen for purine synthesis.

A
  • Glutamine
  • Aspartate
  • Glycine
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13
Q

What is the structure of purine bases?

A

Two rings with two nitrogen groups in each ring

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14
Q

What is the rate limiting enzyme in purine synthesis?

A

Glutamine PRPP amidotransferase

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15
Q

What distinguishes deoxyribonucleotides from ribonucleotides?

A

Deoxyribonucleotides lack a hydroxyl group

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16
Q

How does ribavirin affect purine synthesis?

A

Inhibits IMP dehydrogenase, reducing GMP synthesis

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17
Q

What is the function of mycophenolate?

A

Immunosuppressant that inhibits IMP dehydrogenase

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18
Q

What are the potential fates of free floating purine bases?

A
  • Converted to uric acid
  • Remade into nucleotides (purine salvage)
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19
Q

What enzyme is responsible for converting hypoxanthine or guanine to nucleotides?

A

HGPRT (hypoxanthine guanine phosphoribosyltransferase)

20
Q

What does APRT stand for?

A

Adenine phosphoribosyltransferase

21
Q

What chemotherapy drug mimics hypoxanthine and guanine?

A

6 mercaptopurine

22
Q

What is Azathioprine converted to in the body?

A

6 mercaptopurine

23
Q

What is the significance of PRPP in purine salvage?

A

Combines with free bases to regenerate nucleotides

24
Q

What is the structure of Azathioprine similar to?

A

6MP

Azathioprine has an extra molecule that is removed in the body, resulting in 6MP.

25
Q

What two purines are broken down into uric acid?

A

Hypoxanthine and guanine

These purines are converted to xanthine and then to uric acid for excretion.

26
Q

What enzyme breaks down hypoxanthine into xanthine?

A

Xanthine oxidase

27
Q

What enzyme converts guanine into xanthine?

A

Guanase

28
Q

What is the role of adenosine deaminase?

A

Removes the amine group from adenosine and converts it into inosine

29
Q

What condition is associated with deficiency in adenosine deaminase?

A

Severe combined immunodeficiency syndrome

30
Q

What is gout?

A

A condition caused by excess uric acid in the plasma

31
Q

What are common symptoms of gout?

A

Pain, swelling, and redness in joints

32
Q

What is a classic location for gout symptoms?

A

Base of the big toe

33
Q

What can trigger a gout attack?

A

Under excretion or overproduction of uric acid

34
Q

What dietary factors can contribute to gout?

A

Consumption of purine-rich foods like meats and seafood

35
Q

What medication is used to treat gout?

A

Allopurinol

36
Q

What does allopurinol inhibit?

A

Xanthine oxidase

37
Q

What are the potential effects of co-administering allopurinol with azathioprine or 6MP?

A

Increased effects and toxicity of 6MP

This occurs because allopurinol inhibits the metabolism of these drugs.

38
Q

What is Lesch Nyhan syndrome?

A

A rare disorder caused by absence of the HGPRT enzyme

39
Q

What results from the absence of the HGPRT enzyme?

A

Inability to salvage purines, leading to excess uric acid

40
Q

What are the neurological symptoms associated with Lesch Nyhan syndrome?

A

Hypotonia and choreo

41
Q

What behavior is commonly observed in children with Lesch Nyhan syndrome?

A

Self-mutilating behavior

42
Q

What is a classic presentation of Lesch Nyhan syndrome?

A

A male child with motor symptoms, self-mutilation, and gout

43
Q

Fill in the blank: Adenine is first converted back into the nucleotide _______.

A

Adenosine monophosphate

44
Q

What happens to inosine in the purine breakdown pathway?

A

It is converted into hypoxanthine

45
Q

What is the metabolic pathway that ramps up in Lesch Nyhan syndrome?

A

De novo purine synthesis pathway

Biochemistry (3 decks)

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