Cytochrome P450 enzymes

Question 1

What is the major human cytochrome and why?

Answer 1

The most common human cytochrome is cytochrome P450 3A4, because it can accept a huge range of substrates, different shapes and sizes - its active site can accomodate a wide range of functional groups

Question 2

What is linked with CYP450?

Answer 2

Many side effects can occur with the inhibition or induction of cytochrome P450

Question 3

Where is the two MAIN places 3A4 is found?

Answer 3

The liver and intestinal mucosa

Question 4

Why is grape fruit to be avoided with so many drugs?

Answer 4

Due to it inhibiting CYP 450 3A4 therefore affecting the metabolism of other drugs

Question 5

Why is Grape fruit to be avoided with many Calcium Channel Blockers?

Answer 5

Grapefruit juice will decrease the activity of 3A4, therefore increasing the levels of the drugs in the blood, increasing the chance of side effects.

Question 6

CYP2D6: which drugs have issues with this enzyme and why?

Answer 6

Selective-Seretonin-Reuptake-Inhibitors: SSRIs, these are tricyclic antidepresants like Fluoxetine, Citalopram and these have an affinity for the 2D6 enzyme (this isn’t their mode of action).
If a drug is metabolised by 2D6 e.g Tamoxifen, then an SSRI with a weak affinity to 2D6 will be chosen like Citalopram, to decrease the inhibition of the metabolism of Tamoxifen.

Question 7

What enzyme does broccoli, brussel sprouts and char-grilled meat effect?

Answer 7

CYP450 1A2