Cytochrome P450s in Humans David Nelson Feb. 4, 2009

Human Cytochrome P450s

Lipid metabolismDrug metabolism

CholesterolSteroidsBile AcidsVitamin DFatty AcidsRetinoic AcidProstacyclinsThromboxane A 2

Origin of the P450 name = pigment at 450nm

P450

ER membrane Substrate and O 2

Cytochrome P450 membrane topology

cytosol

NH2

P450

FAD

FMN

NADPH2 e-

NADPH Cytochrome P450Reductase

ER membrane Substrate and O 2

Class II P450 enzymes

cytosol

P450

FAD

FeS

NADPH2 e-

Ferredoxin

Ferredoxin Reductase

Mitochondrial inner membrane

Substrate and O 2

Class I P450 enzymes

matrix

(>55% identity)

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 hydroxylaseCYP19 steroid biosynthesis (1 subfamily, 1 gene) aromatase forms estrogenCYP20 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

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

Human CYP1A2 top and side view, J. Biol. Chem., Vol. 282, 14348-14355, May 11, 2007

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 hydroxylaseCYP19 steroid biosynthesis (1 subfamily, 1 gene) aromatase forms estrogenCYP20 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

The AmpliChip CYP450 array from Roche

The first pharmacogenomics diagnostic chip

3A4 + 3A5

2D6

2C9

2C19

2E1

1A1 1A2 1B1 2A62B6

2C8

Human CYPs contribution to drug metabolism

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.

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).

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

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)

3 7

1224

Cortisol

11-Deoxdycortisol

11-Deoxycorticosterone

Corticosterone

Aldosterone

11A1

CYP17

CYP19

11B1

CYP21

CYP21

11B1

11B2CYP17

CYP17 CYP17

CYP27A1

CYP27B1

active form

CYP24

inactive

24 2627

1

CYP2R1

Human Rat Mouse

CYP2ABFGST

CYP2C

CYP2J

CYP3A

CYP4ABXZ

CYP4F

Total

6 14 13

1 5 9

1 5 8

4 6 8

5 6 10

6 9 9

27 55 72

4 10 15CYP2D