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PHAR 202 > Cytochromes > Flashcards

Cytochromes Flashcards

1
Q

What type of enzyme phase is Cytochrome P450?

A

Major Phase 1 enzyme

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2
Q

What do Cytochromes P450 work on?

A
  • Drugs
  • Poisonous compounds
  • Carcinogens from eating or breathing
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3
Q

What do Cytochromes P450 make?

A

Essential molecules (ie: steroids)

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4
Q

What is the abbreviation for Cytochromes P450?

A

CYP450

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5
Q

What is the definition of isoform?

A

Member of a family based on its homology

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6
Q

What type of enzyme is CYP450?

A

Mono-oxygenases

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7
Q

What protein is associated with CYP450?

A

Integral membrane protein with a single heme group

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8
Q

What membrane is associated with CYP450?

A

Membrane by an N-terminal membrane anchoring sequence

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9
Q

Where can you find CYP450?

A

Systolic side

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10
Q

Where can you find the enzyme systems of CYP450?

A

Endoplasmic reticulum (microsomal; 50/57) and Mitochondria (7/57)

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11
Q

What is the complexity of CYP450?

A

Multi-enzyme complex

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12
Q

What distinguishes Phase 1 from Phase 2?

A

Makes more metabolites that are more polar

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13
Q

Under what conditions will CYP450 take over metabolism of drugs?

A

Hypoxic conditions when there is not enough O2 in the body

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14
Q

What type of metabolism is CYP450 associated with?

A

Xenobiotic metabolism

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15
Q

Where can Lipophilic Xenobiotics be found in?

A

They are found in therapeutic drugs, food additives, and environmental contaminants

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16
Q

True or False: CYP isoforms are discriminating.

A

False: they are less discriminating as they have higher availability, have a variety of substrates, and have multiple sites of oxidation

17
Q

What are the three possible outcomes for the metabolism of xenobiotics and drugs?

A
  1. Inactivation (drug metabolism)
  2. Activation (prodrug conversion: codeine to morphine)
  3. Formation of a highly toxic metabolite (metabolism of acetaminophen to NAPQI)
18
Q

True or False: Xenobiotics/drugs induce CYPs

A

True: CYPs are inducible and inhabitable at the genetic (DNA) level

19
Q

How do CYPs metabolize compounds at a genetic (DNA) level?

A

Via binding cis- and trans- activating elements that cause transcription

20
Q

Which binding is more common in CYPs metabolism?

A

Cis-binding

21
Q

Why is trans-binding less common in CYPs metabolism?

A

Because trans-binding would require the unwinding of the DNA

22
Q

Why can xenobiotics/drugs inhibit CYPs via binding?

A

Because binding would prevent transcription

23
Q

Describe what happens with Rifampicin in relation to CYPs

A

Rifampicin is an anti-tuberculosis drug that upregulates CYP3A4. The rate of metabolism of clearance (of drugs) through the liver increases, which means that the elimination of warfarin increases. This leads to the risk of undertreating patients

24
Q

Describe what happens with St. John’s wort in relation to CYPs

A

St. John’s wort is an herbal medicine that is believed to treat mild depression without the need of a prescription. It induces CYP3A4

25
Q

Describe what happens with grapefruit juice in relation to CYPs

A

Drinking more than 200 mL of grapefruit juice induces CYP3A4, which means that it induces the actions of the enzyme

26
Q

What are the relations between enzymes, drugs, clearance, and effects?

A

Increase in enzyme leads to an increase in clearance. An increase in clearance leads to a decrease in the amount of drugs in the body. A decrease in the drugs in the body leads to a decrease in the drug’s effects

27
Q

What are the three types of enzymes as described by Olga Greengard?

A

Type I, Type II, Type III

28
Q

Describe what a Type I enzyme is

A

Type I enzymes are higher in fetus than in adults

29
Q

True or False: Type II enzymes only arise after birth

A

False: Type II enzymes are enzymes that are the same through life

30
Q

What is a Type III enzyme?

A

Type III enzymes are enzymes that arise after birth

31
Q

In what way is Greengard’s description useful?

A

It helps with the classification systems of enzymes

32
Q

How is Greengard’s description on enzymes inaccurate?

A

The description cannot be pan-specific since it is known that there are enzymes that peak in adolescence

PHAR 202 (8 decks)

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