1. Cytochrome P450s in Humans David Nelson Feb. 4, 2009

2. Human Cytochrome P450s Drug metabolism Lipid metabolism Cholesterol
Steroids
Bile Acids
Vitamin D
Fatty Acids
Retinoic Acid
Prostacyclins
Thromboxane A 2

3. Origin of the P450 name = pigment at 450nm

7. Cytochrome P450 membrane topology
cytosol
ER membrane
Substrate and O 2 NH 2
Cytochrome P450 membrane topology

10. NADPH NADPH Cytochrome P450 - 2 e Reductase P450 cytosol ER membrane
FAD
Reductase
FMN
P450
cytosol
ER membrane
Substrate and O 2
Class II P450 enzymes

11. Mitochondrial inner membrane Substrate and O
NADPH
Ferredoxin Reductase -
2 e
FAD
Ferredoxin
FeS
P450
matrix
Mitochondrial inner membrane
Substrate and O 2
Class I P450 enzymes

12. (>55% identity)

13. Humans have 18 families of cytochrome P450 genes and 44 subfamilies
CYP1 drug metabolism (2 subfamilies, 3 genes, 1 pseudogene)
CYP2 drug, steroid, vitamin D metabolism (13 subfamilies, 16 genes, 16 pseudogenes)
CYP3 drug metabolism (1 subfamily, 4 genes, 2 pseudogenes)
CYP4 arachidonic acid or fatty acid metabolism (6 subfamilies, 12 genes, 10 pseudogenes)
CYP5 Thromboxane A2 synthase (1 subfamily, 1 gene)
CYP7A bile acid biosynthesis 7-alpha hydroxylase of steroid nucleus (1 subfamily member)
CYP7B brain specific form of 7-alpha hydroxylase (1 subfamily member)
CYP8A prostacyclin synthase (1 subfamily member)
CYP8B bile acid biosynthesis (1 subfamily member)
CYP11 steroid biosynthesis (2 subfamilies, 3 genes)
CYP17 steroid biosynthesis (1 subfamily, 1 gene) 17-alpha hydroxylase
CYP19 steroid biosynthesis (1 subfamily, 1 gene) aromatase forms estrogen
CYP20 Unknown function (1 subfamily, 1 gene)
CYP21 steroid biosynthesis (1 subfamily, 1 gene, 1 pseudogene)
CYP24 vitamin D degradation (1 subfamily, 1 gene)
CYP26A retinoic acid hydroxylase important in development (1 subfamily member)
CYP26B retinoic acid hydroxylase (1 subfamily member)
CYP26C retinoic acid hydroxylase (1 subfamily member)
CYP27A bile acid biosynthesis (1 subfamily member)
CYP27B Vitamin D3 1-alpha hydroxylase activates vitamin D3 (1 subfamily member)
CYP27C unknown function(1 subfamily member)
CYP39 7 alpha hydroxylation of 24 hydroxy cholesterol (1 subfamily member)
CYP46 cholesterol 24-hydroxylase (1 subfamily member)
CYP51 cholesterol biosynthesis (1 subfamily, 1 gene, 3 pseudogenes) lanosterol 14-alpha demethylase
blue = mitochondrial

14. Induction of Cytochrome P450 Genes
endocrine control ACTH (steroid biosynthesis P450s)
PPAR peroxisome proliferators (clofibrate) CYP4 family
PXR CYP3 family
CAR phenobarbital CYP2B 40-50X in rats
AHR (benzo-a-pyrene, cigarette smoke) CYP1 family
ethanol CYP2E1 enzyme stabilization by substrate

16. Human CYP1A2 top and side view, J. Biol. Chem. , Vol
Human CYP1A2 top and side view, J. Biol. Chem., Vol. 282, , May 11, 2007

17. Humans have 18 families of cytochrome P450 genes and 43 subfamilies
CYP1 drug metabolism (2 subfamilies, 3 genes, 1 pseudogene)
CYP2 drug, steroid, vitamin D metabolism (13 subfamilies, 16 genes, 16 pseudogenes)
CYP3 drug metabolism (1 subfamily, 4 genes, 2 pseudogenes)
CYP4 arachidonic acid or fatty acid metabolism (5 subfamilies, 11 genes, 10 pseudogenes)
CYP5 Thromboxane A2 synthase (1 subfamily, 1 gene)
CYP7A bile acid biosynthesis 7-alpha hydroxylase of steroid nucleus (1 subfamily member)
CYP7B brain specific form of 7-alpha hydroxylase (1 subfamily member)
CYP8A prostacyclin synthase (1 subfamily member)
CYP8B bile acid biosynthesis (1 subfamily member)
CYP11 steroid biosynthesis (2 subfamilies, 3 genes)
CYP17 steroid biosynthesis (1 subfamily, 1 gene) 17-alpha hydroxylase
CYP19 steroid biosynthesis (1 subfamily, 1 gene) aromatase forms estrogen
CYP20 Unknown function (1 subfamily, 1 gene)
CYP21 steroid biosynthesis (1 subfamily, 1 gene, 1 pseudogene)
CYP24 vitamin D degradation (1 subfamily, 1 gene)
CYP26A retinoic acid hydroxylase important in development (1 subfamily member)
CYP26B retinoic acid hydroxylase (1 subfamily member)
CYP26C retinoic acid hydroxylase (1 subfamily member)
CYP27A bile acid biosynthesis (1 subfamily member)
CYP27B Vitamin D3 1-alpha hydroxylase activates vitamin D3 (1 subfamily member)
CYP27C unknown function(1 subfamily member)
CYP39 7 alpha hydroxylation of 24 hydroxy cholesterol (1 subfamily member)
CYP46 cholesterol 24-hydroxylase (1 subfamily member)
CYP51 cholesterol biosynthesis (1 subfamily, 1 gene, 3 pseudogenes) lanosterol 14-alpha demethylase
blue = mitochondrial

18. The AmpliChip CYP450 array from Roche
The first pharmacogenomics diagnostic chip

19. Human CYPs contribution to drug metabolism
3A4 + 3A5
2C19
2D6
2E1
Human CYPs contribution to drug metabolism

20. CYP2D6 Substrates
* Antiarrhythmics: Flecainide, Mexiletine,
Propafenone
* Antidepressants: Amitriptyline, Paroxetine,
Venlafaxine, Fluoxetine (Prozac), Trazadone
* Antipsychotics: Clorpromazine, Haloperidol,
Thoridazine
* Beta-Blockers: Labetalol, Timolol, Propanolol,
Pindolol, Metoprolol
* Analgesics: Codeine, Fentanyl, Meperidine,
Oxycodone, Propoxyphene
oxycodone is oxycontin, a favorite drug of abuse.

21. CYP3A4 Substrates
* Acetominophen (Tylenol)
* Codeine (narcotic)
* Cyclosporin A (an immunosuppresant),
* Diazepam (Valium)
* Erythromycin (antibiotic)
* Lidocaine (anaesthetic),
* Lovastatin (HMGCoA reductase inhibitor,
a cholesterol lowering drug),
* Taxol (cancer drug),
* Warfarin (anticoagulant).

22. CASE REPORT:
Man, 63, had been receiving medication for major
depression, boarded flight from Toronto, Canada to
London, UK. Upon arrival - passenger in seat 83A
found unrousable
Carry-on bag:
Mefadazone (used for > 1 mo., for depression
Ketoconazole (fungal infection, 6 - mo. supply)
Triazolam (antipsychotic, insomnia, ? taken)
Reason: DRUG INTERACTIONS
ALL THREE DRUGS - BIND TO CYP3A4
Result of concomitant medication
DRUG INTERACTIONS -
any change of therapeutic effectiveness or
toxicity caused by concomitant uptake of two
or more drugs

23. Terfenadine vs. ketoconazole: 15 to 72X
increase of AUC (area under the curve) of
terfenadine (CYP3A4) (Honig et al. 1993)
Venlafaxine/quinidine: up to 20X
increase of AUC venlafaxine (CYP2D6)
subgroup of extensive metabolizers:
0.5 to 10X change of venlafaxine AUC
(Lessard et al. 1999)

26. 24 12 3 7

27. CYP21 11A1 11B1 CYP17 CYP17 11B2 CYP21 CYP17 CYP17 11B1 CYP19
11-Deoxycorticosterone
11B1
Corticosterone
CYP17
CYP17
11B2
Aldosterone
CYP21
CYP17
CYP17
11-Deoxdycortisol
11B1
CYP19
Cortisol

28. 24 26 27
CYP27A1 1
CYP2R1
CYP27B1
CYP24
active form
inactive

29. Human Rat Mouse
CYP2ABFGST
CYP2C
CYP2D
CYP2J
CYP3A
CYP4ABXZ
CYP4F
Total