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Biochem 4 > Purine metabolism > Flashcards

Purine metabolism Flashcards

exam 4

1
Q

ribose and base

A

nucleosides

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2
Q

ribose and base and phosphate

A

nucleotides

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3
Q

how can nucleotides be acquired?

A

salvage pathway or de Novo synthesis

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4
Q

used for DNA, RNA or high energy intermediates

A

nucleotides

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5
Q

aspartate, CO2, glycine, Glutamine x 2, N10-formyl-tetrahydrofolate

A

purines derivations

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6
Q

purine synthesis begins with _______ and the formation of phosphoribosyl-1-pyrophosphate and 5- phosphoribosylamine

A

ribose-5-p

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7
Q

ribose-5-p reacts with ATP and PRPP synthetase to form

A

PRPP

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8
Q

used to create ribose-5-p

A

PPP

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9
Q

PRPP reacts with _________ and amidophosphoribosyl transferase to form

A

glutamine to form 5-phosphoribosylamine

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10
Q

which is the highly regulates step in which the glycosidic bond is formed

A

PRPP + Glutamine–> 5-phosphoribosylamine

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11
Q

5-phosphoribosylamine reacts with _____ and ATP to form Ribose-P-Glycinamide ribonucleotide

A

glycine

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12
Q

Ribose-P-Glycinamide ribonucleotide reacts with _________ to form Ribose-P-formylglycinAMIDE ribonucleotide

A

N10-Formyl-THF

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13
Q

Ribose-P-Glycinamide ribonucleotide reacts with __________ and ATP to form Ribose-P-GlycinamIDINE ribonucleotide

A

Glutamine

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14
Q

loss of ______ results in Ribose-P-5 aminoimidazole ribonucleotide

A

H2O

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15
Q

carry out various methylation reactions and the one used in purine synthesis

A

folates and N10 formyl-THF

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16
Q

5-Aminoimidazole-4-Carboxylate Ribonucleotide reacts with __________ and ATP to form 5-Aminoimidazole-4-N-Succinocarboxamide Ribonucleotide

A

Aspartate

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17
Q

9.5-Aminoimidazole-4-N-Succinocarboxamide Ribonucleotide reacts and LOSES ________ to form 5-Aminoimidazole-4-Carboxamide Ribonucleotide

A

Fumarate

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18
Q

Ribose-P-5-Aminoimidazole-Ribonucleotide loses _______ to form 5-Aminoimidazole-4-Carboxylate Ribonucleotide

A

CO2

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19
Q

5-Aminoimidazole-4-Carboxamide Ribonucleotide reacts with ___________ to form 5-Formamidoimidazole-4-Carboxamide Ribonucleotide

A

N10-FORMYL-THF

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20
Q

Loss of H2O from 5-Formamidoimidazole-4-Carboxamide Ribonucleotide results in formation of

A

INOSINATE

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21
Q

IMP serves as a precursor for either

A

AMP or GMP

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22
Q

synthesis of AMP requires

A

GTP

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23
Q

Synthesis of GMP requires

A

ATP

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24
Q

IMP reacts _____ and GTP to form intermediate then forms AMP

A

aspartate

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25
Q

IMP reacts with _____ to form intermediate and then reacts with ____ and ATP to form GTP

A

IMP reacts with NAD+ and then with Glutamine

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26
Q

True or False: production of one purine nucleoside ihibits the production of the other

A

FALSE–> insures

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27
Q

conversion of Monophosphates to Diphosphates are done by _____ that are BASE-SPECIFIC; but not ______

A

KINASES that are not SUGAR-SPECIFIC

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28
Q

Nucleoside Diphosphate is converted to ______ by Nucleoside Diphosphate Kinase

A

TRIPHOSPHATE

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29
Q

Nucleoside Diphosphate Kinase

A

enzyme has broad-specificity

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30
Q

Enzymes needed for purine biosynthesis are in the

A

cytosol

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31
Q

de novo synthesis occurs actively in the

A

liver and placenta

32
Q

Degraded cells in the body have their nucleotides reused

A

salvage pathway

33
Q

Many chemotherapeutics or anti-viral agents are ____________ that are incorporated via salvage pathway

A

NUCLEOTIDE ANALOGUES

34
Q

*BOTH De Novo Synthesis and Salvage Pathway begin with activated

A

PRPP

35
Q

In the gut, the pancreas secretes

A

NUCLEASES and PHOSPHODIESTERASE

36
Q

produce short oligonucleotides;

A

nucleases

37
Q

produces mononucleotides

A

phosphodiesterase

38
Q

In the gut, Nucleotidases cleave off Pi to form

A

Nucleoside

39
Q

will cleave off sugar to give either PURINE/PYRIMIDINE

A

Nucleosidase

40
Q

excess purines and pyrimidines are turned into

A

uric acid then urine

41
Q

GUANINE + PRPP → GMP + PPi

catalyzed by:

A

HGPRT

42
Q

HYPOXANTHINE + PRPP → IMP +PPi

catalyzed by:

A

HGPRT

43
Q

ADENINE + PRPP → AMP + PPi

catalyzed by:

A

APRT

44
Q

AMP & GMP will inhibit the ___________ and STOP the conversion of IMP to their respective base

A

IMP branch point

45
Q

Salvage Pathway begins with formation of AMP + GMP, thus SALVAGE PATHWAY SHUTS OFF

A

DE NOVO BIOSYNTHESIS

46
Q

PRPP will ______ its own conversion to 5-Phosphoribosylamine via activation of Amidophoshporibosyl Transferase

A

activate

47
Q

promotes synthesis of the other respective base

A

ATP/GTP

48
Q

ADP/GDP will ______ conversion to ribose 5 P to PRPP

A

inhibit

49
Q

AMP, ADP, ATP/GMP,GDP,GTP will FEEDBACK ________ PRPP conversion to 5-Phosphoribosylamine, via action on Amidophoshporibosyl Transferase

A

inhibit

50
Q

expensive pathway

A

de novo biosynthesis

51
Q

begins when PRPP levels accumulate and are excess

A

De Novo Biosynthesis

52
Q

Nucleoside is converted into _______ via Adenosine Deaminase

A

INOSINE

53
Q

INOSINE (nucleoside) is cleaved to form ______________ and Ribose-1-P under action of Purine Nucleoside Phosphorylase

A

Hypoxanthine

54
Q

Nucleotides have a _________ thus they must be controlled and excreted carefully

A

nitrogen component

55
Q

In general, nucleotides are excreted as

A

uric acid

56
Q

Hypoxanthine is converted to Xanthine and then Uric Acid; both reactions are done by

A

Xanthine Oxidase

57
Q

_____ is converted to Xanthine by Guanine Deaminase, then converted to Uric Acid by Xanthine Oxidase

A

Guanine

58
Q

is characterized by ELEVATED URIC ACID levels in blood due to many metabolic abnormalities

A

Gout

59
Q

In Gout, ______ are deposited in cartilage of joints and in the kidney, resulting in pain and disability

A

Urate Crystals

60
Q

Gout is defective in [3]

A

HGRT and PRPP synthetase and Glucose 6 Phosphatase

61
Q

Defective HGPRT means buildup of

A

Guanine + Hypoxanthine

62
Q

PRPP will accumulate due to INACTIVATION of SALVAGE and thus causes

A

DE NOVO ACTIVATION

63
Q

Lower levels of purines also cause less

A

feedback inhibitions

64
Q

defective PRPP synthetase leads to

A

Enzyme no longer is susceptible to inhibition by purine nucleotides

65
Q

Defective_______means increased use of PPP and excess production of Ribose-5-P, the PRPP precursor

A

defective glucose 6 phosphatase

66
Q

Allopurinol is a competitive inhibitor of

A

Xanthine Oxidase

67
Q

Drug keeps Uric Acid levels LOW; Xanthine and Hypoxanthine are excreted in urine

A

gout tx

68
Q

Gout tends to accumulate in the extremities which are more

A

temperature sensitive

69
Q

x-linked disorder lacking functional HGPRT

A

Lesh-Nyan syndrome

70
Q

Self-mutilation, mental illness and gout like symptoms and leads to Increase in rate of purine biosynthesis by De Novo Pathway

A

Lesh-Nyan syndrome

71
Q

HGPRT activity is highest in _________ suggesting importance of purine salvage pathway in this tissue

A

brain

72
Q

what removes amine off nucleoside to form Inosine

A

Adenosine Deaminase

73
Q

ADA causes _________- because of lack of B cells and Tcells

A

SEVERE COMBINED IMMUNODEFICIENCY

74
Q

resemble para-Aminobenzoic and thus INHIBIT FOLATE SYNTHESIS and stop purine synthesis

A

Sulfonamides

75
Q

Used in chemotherapy for treatment of Acute Leukemia

A

6-Mercaptopurine

76
Q

6-Mercaptopurine Functions as a _______ prevents production of AMP and GMP

A

hypoxanthine analogue

Biochem 4 (8 decks)

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