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Drugs and Toxicology > Metabolic Phases: Phase I > Flashcards

Metabolic Phases: Phase I Flashcards

1
Q

What is Phase I ?

A

Alteration of the original compound that expose the xenobiotic to –OH, -NH2, -SH and -COOH functional groups.

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2
Q

Phase I involves

A
  1. Hydrolysis
  2. Reduction
  3. Oxidation
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3
Q

What is Hydrolysis?

A

This is the process by which cleavage occurs due to the addition of water.

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4
Q

What functional group can all be metabolized by hydrolysis.

A

Esters, amides, hydrazides, and carbamates

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5
Q

The enzymes that catalyse these hydrolytic reactions

A

Carboxylesterases and amidases,

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6
Q

Where are typically hydrolytic enzymes found ?

A

in the cytosol, but microsomal esterases and amidases have been described, and some are also found in plasma.

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7
Q

Carboxylesterases have

A

amidase activity

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8
Q

Amidases have

A

esterase activity.

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9
Q

Hydrolysis of esters is usually done by

A

esterases.

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10
Q

Where is esterases found?

A

They are usually found in the blood, but can be found in tissues such as the liver as well.

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11
Q

3 Classes of esterases.

A
  1. A-esterases include arylesterase and paraoxonase (lactonase).
  2. B-esterases include carboxylesterase and cholinesterase. They are inhibited by paraoxon.
  3. C-esterases acetylesterase as their substrate prefered is acetyl esters. They are not inhibited by paraoxon.
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12
Q

Esterase activity is important to the _____ and the ____ of _____.

A

Esterase activity is important in both the detoxication and toxicity of organophosphates.

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13
Q

Acetylcholinesterase is inhibited by organophosphates such as _____ and _____.

A

paraoxon and malaoxon.

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14
Q

What is malathon?

A

Malathion, a widely used insecticide, is primarily metabolised by carboxylesterase in mammals, which is a detoxication route.

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15
Q

Pesticide Metabolites Paraoxon and Malaoxon Cause

A

Cellular Death in Cultured Human Pulmonary Cells via Different Mechanisms

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16
Q

Organophosphorus (OP) pesticides are known to induce

A

pulmonary toxicity in both humans and experimental animals.

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17
Q

The effects of parathion and malathion, as well as their respective metabolites, paraoxon and malaoxon, on primary cultured human large and small airway cells were studied

A

to elucidate the mechanism of OP-induced cytotoxicity.

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18
Q

Following a 24-hour exposure to paraoxon and malaoxon, there

A

was a dose-dependent increase in cytotoxicity.

19
Q

Treatment with parathion or malathion had

A

no effect at clinically relevant concentrations.

20
Q

Caspase activation was induced by_____ exposure, but not by ______exposure.

A

Caspase activation was induced by paraoxon exposure, but not by malaoxon exposure.

21
Q

Caspase inhibition with drugs protected against

A

paraoxon-induced cell death but not malaoxon-induced cell death.

21
Q

Caspase inhibition with drugs protected against

A

paraoxon-induced cell death but not malaoxon-induced cell death.

22
Q

The hydrolysis of amides are catalysed

A

by amidases in the liver, but can be done also by plasma esterases.

23
Q

The ester functional group made from

A

an ether and Carboxylic acid

24
Q

The amide functional group made from

A

an amine and Carboxylic acid

25
Q

The hydrolysis of esters and amides occur

A

when a nucleophile electron rich specie such as water or hydroxyl ion

26
Q

What is reduction?

A

This is the process by which a compound gains
1. Electron
2. Hydrogen
3. Loses oxygen

27
Q

Aldehyde, ketones, disulfides, sulfoxides or basically nitrogen containing groups

A

undergo reduction.

28
Q

Aldehyde, ketones, disulfides, sulfoxides or basically nitrogen containing groups broken down by

A

enzymatic agents and non-ezymatic agents.

29
Q

What are enzymatic agents ?

A

Cytochrome P450

30
Q

What are non enzymatic agents?

A

Nonezymatic agents – Gut microflora, FAD (Flavin Adenine Dinucelotide), NADP (Nicotineamide Adenine Dinucelotide Phosphate)

31
Q

Reductions Reactions Focused on

A
  1. Azo- and Nitro- Reduction
  2. Carbonyl Reduction
  3. Disulfide Reduction
  4. Dehalogenation
32
Q

What is oxidation?

A

This is the process by which a compound loses an electron, gains oxygen and hydrogen.

33
Q

Many of the enzymes mentioned in reduction perform oxidation as well such as

A

Cytochrome P450, alcohol dehydrogenase and aldehyde dehydrogenase.

34
Q

Oxidation Reactions Focused on

A
  1. Dealkylation
  2. Desulfation
  3. Oxidation of alcohol
35
Q

What is Dealkylation?

A

The process of removing an alkyl group from nitrogen (N), sulfur (S) and oxygen (O) atoms. This is done by microsomal enzymes. A corresponding aldehyde is a result of the reaction.

36
Q

What is Desulfuration?

A

The process of replacing sulfur with oxygen.

37
Q

Parathion is

A

an insecticide (organophosphate)

38
Q

What happens when parathion enters the body?

A

When in the body the reaction appears to be catalysed by either cytochromes P-450 or the FAD-containing monooxygenases and therefore requires NADPH and oxygen.

39
Q

What is the more toxic compound of parathion and why is this bad for the bod?y

A

paraoxon which can inhibit cholinesterase

40
Q

Oxidation in alcohol can occur by

A

By two ways:
1. Microsomal enzyme activity by Cytochrome P450
2. Non microsomal enzyme activity by alcohol dehydrogenase (ADH) and is the major pathway

41
Q

Why would NAD be used to aid ADH than NADPH?

A

ADH uses the aid of NAD, but NADPH can be used as well but the reaction would be slower.

42
Q

The NAD enzyme works on

A

both primary and secondary alcohols, with primary ones having a faster reaction.

43
Q

Primary & Secondary Alcohols are converted in to their respective aldehydes
which are further converted

A

to respective acids by aldehyde dehydrogenase (ALDH).

Drugs and Toxicology (14 decks)

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