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NUTR 4510- Food, Tox, Nutrition > Phase II reactions > Flashcards

Phase II reactions Flashcards

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1
Q

phase II is also known as what

A

conjugation

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2
Q

what is a reducing agent

A

molecule that donates e to another molecule or atom

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3
Q

what is an oxidizing agent

A

molecule that accepts e from another molecule

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4
Q

what is an electrophile

A

e poor (looking to accept e)

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5
Q

what is a nucleophile

A

e rich (looking to donate e)

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6
Q

electrophiles undergo phase II metabolism by?

A

glutathione conjugation

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7
Q

what is the conjugating agent of glutathione conjugation

A

glutathione (GSH)

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8
Q

what is the conjugating enzyme of glutathione conjugation

A

glutathione-s-transferase

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9
Q

nucleophiles can undergo phase II metabolism by?

A
  1. sulfate conjugation

2. glucuronide conjugation

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10
Q

what is the conjugating agent of sulphate conjugation

A

phosphoadenosine phosphosulfate (PAPS)

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11
Q

what is the conjugating enzyme of sulfate conjugation

A

sulfotransferase (SULT)

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12
Q

what is the conjugating agent of glucuronide conjugation

A

UDP glucuronic acid (ADPGA)

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13
Q

what is the conjugating enzyme in glucuronide conjugation

A

UDP-glucoronyl transferase (UDPGT)

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14
Q

describe glutathione conjugation

A

route of conjugation of a vartety of electrophile C and endogenous substrates

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15
Q

what are examples of electrophilic X

A

PAH, HCA, aflatoxin

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16
Q

glutathione (GSH) production is dependent on?

A

GSH production is dependent upon suffer amino acid synthesis

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17
Q

what is the process of glutathione conjugation

A
  1. GST conjugated reactive electrophile with GSH to form a glutathione conjugate
  2. the glutathione conjugate is lipophilic, so some may partition to bile and can be excreted in feces or enterohepatic circulation
  3. or, the glutathione conjugate may be metabolized by peptidases, removing glutamate and glycine to form cyctein conjugate (which is more hydrophilic)
  4. or, N-acetyltransferase may add acetyl group to the cysteine conjugate, forming a mercapturic acid conjugate (very hydrophilic)
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18
Q

how is glutathione regenerated

A

the pentose phosphate pathway (HMP shut) regenerated NADPH

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19
Q

an increased GSSH to GSH ratio?

A

is an indication of oxidative stress

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20
Q

what is the route of most nucleophilic conjugation

A

glucoronide conjugation

21
Q

when is UDP glucuronic acid (UDPGA) abundant

A

after a carbohydrate-rich meal when dietary X may be present

22
Q

what is UDPGA made of

A

UDP-glucose (an intermediate in glycogen synthesis)

23
Q

how does the conjugating enzyme for glucoronide conjugation, UDPGT) work

A

cleaves high energy bond between UDP and glucuronic acid

24
Q

what is glucuronidation

A

glucuronide conjugation

25
Q

describe excretion of glucuronide conjugates

A
  • high molecular weight, low water solubility:
  • partition into bile
  • excreted via feces or return to the liver via EHC

Low molecular weight, high water solubility
- excreted via urine

26
Q

if a glucuronide conjugate is high molecular weight with low water solubility where does it go

A
  • partitions into bile

- excreted via feces or return to the liver via EHC

27
Q

if a glucuronide conjugate is low molecular weight with high water solubility

A
  • excreted via urine
28
Q

what is the main site of action of glucuronidation

A

liver

if reaction occurs in the muscle there is no immediate access to EHC

29
Q

describe the glucuronidaton of morphine

A
  • as a nucleophile, glucuronidation at either the 3- or 6- position
30
Q

what blocks route of excretion of morphine

A

synthetic acytylation at either the 3- or 6- position (heroin)

31
Q

what is sulfation

A

sulfate conjugation

32
Q

when does salvation happen

A

route of some nucleophilic X conjugation as well as conjugation of endogenous substrates (steroid)

33
Q

what is the conjugating agent of sulfation

A

phosphoadenosine phosphosulfate

34
Q

what is PAPS dependent on

A

dependent on sulphur amino acid status

35
Q

where are sulfotransferases found

A

highest expression in reproductive tissues

36
Q

when does acetylation conjugation

A

route of conjugation for aromatic amines

37
Q

for substrates like caffeine, what does acetylation produce

A

stable conjugate for excretion

38
Q

for PhIP, what does acetylation produce

A

a reactive electrophile (primary carcinogen)

39
Q

when is acetyl-CoA abundant

A

after a meal

40
Q

what is the influence of protein deficiency on sulfation

A
  • sensitive to sulphur amino acid status

- leads to decreased sulfation capability

41
Q

what is the influence of protein deficiency on glutathione conjugation

A
  • GSH is an essential intracellular reducing agent so it is maintained at a certain level despite decreased SAA status
  • as protein deficiency becomes more severe eventually lose GSH production/availability
42
Q

what is the influence of starvation on glutathione conjugation

A
  • decreased GSH production with less availability of amino acid constituents
  • increased GST production
43
Q

what is the influence of starvation on glucuronidation

A
  • decreased UDPGS production with less flux of carbohydrate to glycogen
44
Q

what foods contain methionine (MET)

A
  • eggs, dairy, animal proteins

- sesame

45
Q

is acetaminophen an electrophile or nucleophile

A

nucleophile

46
Q

what can acetaminophen be conjugated by

A

glucuronidation
sulfation

then excreted by urine

47
Q

explain mechanism that acetaminophen metabolism leads to liver cell death

A

some acetaminophen pool is metabolized by CYP to a reactive electrophile
- which attacks SH groups leading to liver cell death

48
Q

what are the physiological changes associated with obesity that may affect drug toxicity

A
  • increased circulating blood volumes and hemodynamic changes
  • increased risk of cardiomyopathy and atherosclerosis
  • alterations in pulmonary function
  • changes in large airway anatomy
49
Q

explain how hydrophilic xenobiotics change with obesity

A
  • the hydrophilic xenobiotics remain in the circulation more readily and will have slower distribution to the tissues

NUTR 4510- Food, Tox, Nutrition (5 decks)

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