Cytochrome P450 2B6 is an enzyme

Enzyme

Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...

 that in humans is encoded by the CYP2B6 gene

Gene

A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...

. CYP2B6 is a member of the Cytochrome P450 group of enzymes. Along with CYP2A6

CYP2A6

Cytochrome P450 2A6 is a member of the cytochrome P450 mixed-function oxidase system, which is involved in the metabolism of xenobiotics in the body. CYP2A6 is the primary enzyme responsible for the oxidation of nicotine and cotinine. It is also involved in the metabolism of several...

, it is involved with metabolizing nicotine

Nicotine

Nicotine is an alkaloid found in the nightshade family of plants that constitutes approximately 0.6–3.0% of the dry weight of tobacco, with biosynthesis taking place in the roots and accumulation occurring in the leaves...

, along with many other substances.

Function

This gene, CYP2B6, encodes a member of the cytochrome P450 superfamily of enzymes. The cytochrome P450 proteins are monooxygenase

Monooxygenase

Monooxygenases are enzymes that incorporate one hydroxyl group into substrates in many metabolic pathways. In this reaction, two atoms of dioxygen are reduced to one hydroxyl group and one H2O molecule by the concomitant oxidation of NADH.-Classification:...

s which catalyze many reactions involved in drug metabolism

Metabolism

Metabolism is the set of chemical reactions that happen in the cells of living organisms to sustain life. These processes allow organisms to grow and reproduce, maintain their structures, and respond to their environments. Metabolism is usually divided into two categories...

 and synthesis of cholesterol, steroids and other lipids. This protein localizes to the endoplasmic reticulum

Endoplasmic reticulum

The endoplasmic reticulum is an organelle of cells in eukaryotic organisms that forms an interconnected network of tubules, vesicles, and cisternae...

 and its expression is induced by phenobarbital

Phenobarbital

Phenobarbital or phenobarbitone is a barbiturate, first marketed as Luminal by Friedr. Bayer et comp. It is the most widely used anticonvulsant worldwide, and the oldest still commonly used. It also has sedative and hypnotic properties but, as with other barbiturates, has been superseded by the...

. The enzyme is known to metabolize some xenobiotic

Xenobiotic

A xenobiotic is a chemical which is found in an organism but which is not normally produced or expected to be present in it. It can also cover substances which are present in much higher concentrations than are usual...

s, such as the anti-cancer drugs cyclophosphamide and ifosphamide.

Gene

Transcript variants for this gene have been described; however, it has not been resolved whether these transcripts are in fact produced by this gene or by a closely related pseudogene

Pseudogene

Pseudogenes are dysfunctional relatives of known genes that have lost their protein-coding ability or are otherwise no longer expressed in the cell...

, CYP2B7. Both the gene and the pseudogene are located in the middle of a CYP2A pseudogene found in a large cluster of cytochrome P450 genes from the CYP2A, CYP2B and CYP2F subfamilies on chromosome 19q.

CYP2B6 Ligands

Following is a table of selected substrates, inducers

Enzyme induction and inhibition

Enzyme induction is a process in which a molecule induces the expression of an enzyme.Enzyme inhibition can refer to* the inhibition of the expression of the enzyme by another molecule...

 and inhibitors

Enzyme induction and inhibition

Enzyme induction is a process in which a molecule induces the expression of an enzyme.Enzyme inhibition can refer to* the inhibition of the expression of the enzyme by another molecule...

 of CYP2B6.

Inhibitors of CYP2B6 can be classified by their potency

Potency (pharmacology)

In the field of pharmacology, potency is a measure of drug activity expressed in terms of the amount required to produce an effect of given intensity. A highly potent drug evokes a larger response at low concentrations, while a drug of lower potency evokes a small response at low concentrations...

, such as:

• Strong inhibitor being one that causes at least a 5-fold increase in the plasma AUC values, or more than 80% decrease in clearance
  Clearance (medicine)
  In medicine, the clearance is a measurement of the renal excretion ability. Although clearance may also involve other organs than the kidney, it is almost synonymous with renal clearance or renal plasma clearance. Each substance has a specific clearance that depends on its filtration characteristics...
  
  .
• Moderate inhibitor being one that causes at least a 2-fold increase in the plasma AUC values, or 50-80% decrease in clearance.
• Weak inhibitor being one that causes at least a 1.25-fold but less than 2-fold increase in the plasma AUC values, or 20-50% decrease in clearance.

Substrates	Inhibitors	Inducers
Bupropion Bupropion Bupropion is an atypical antidepressant and smoking cessation aid. The drug is a non-tricyclic antidepressant and differs from most commonly prescribed antidepressants such as SSRIs, as its primary pharmacological action is thought to be norepinephrine-dopamine reuptake inhibition...  (antidepressant Antidepressant An antidepressant is a psychiatric medication used to alleviate mood disorders, such as major depression and dysthymia and anxiety disorders such as social anxiety disorder. According to Gelder, Mayou &*Geddes people with a depressive illness will experience a therapeutic effect to their mood;... ) Cyclophosphamide Cyclophosphamide Cyclophosphamide , also known as cytophosphane, is a nitrogen mustard alkylating agent, from the oxazophorines group....  (Alkylating antineoplastic agent Alkylating antineoplastic agent An alkylating antineoplastic agent is an alkylating agent used in cancer treatment that attaches an alkyl group to DNA.The alkyl group is attached to the guanine base of DNA, at the number 7 nitrogen atom of the purine ring.... ) Efavirenz Efavirenz Efavirenz is a non-nucleoside reverse transcriptase inhibitor and is used as part of highly active antiretroviral therapy for the treatment of a human immunodeficiency virus type 1....   (NNRTI) Ifosfamide Ifosfamide Ifosfamide is a nitrogen mustard alkylating agent used in the treatment of cancer.It is sometimes abbreviated "IFO".-Uses:It is given as a treatment for a variety of cancers, including:...   (Alkylating antineoplastic agent Alkylating antineoplastic agent An alkylating antineoplastic agent is an alkylating agent used in cancer treatment that attaches an alkyl group to DNA.The alkyl group is attached to the guanine base of DNA, at the number 7 nitrogen atom of the purine ring.... ) Nevirapine (NNRTI) Propofol Propofol Propofol is a short-acting, intravenously administered hypnotic agent. Its uses include the induction and maintenance of general anesthesia, sedation for mechanically ventilated adults, and procedural sedation. Propofol is also commonly used in veterinary medicine...  (anesthetic) tamoxifen Tamoxifen Tamoxifen is an antagonist of the estrogen receptor in breast tissue via its active metabolite, hydroxytamoxifen. In other tissues such as the endometrium, it behaves as an agonist, hence tamoxifen may be characterized as a mixed agonist/antagonist...  (SERM Selective estrogen receptor modulator Selective Estrogen Receptor Modulators are a class of compounds that act on the estrogen receptor. A characteristic that distinguishes these substances from pure receptor agonists and antagonists is that their action is different in various tissues, thereby granting the possibility to selectively... ) Valproic acid Valproic acid Valproic acid is a chemical compound that has found clinical use as an anticonvulsant and mood-stabilizing drug, primarily in the treatment of epilepsy, bipolar disorder, and, less commonly, major depression. It is also used to treat migraine headaches and schizophrenia...  (anticonvulsant Anticonvulsant The anticonvulsants are a diverse group of pharmaceuticals used in the treatment of epileptic seizures. Anticonvulsants are also increasingly being used in the treatment of bipolar disorder, since many seem to act as mood stabilizers, and in the treatment of neuropathic pain. The goal of an... Alfentanil Alfentanil Alfentanil is a potent but short-acting synthetic opioid analgesic drug, used for anaesthesia in surgery. It is an analogue of fentanyl with around 1/4 the potency of fentanyl and around 1/3 of the duration of action, but with an onset of effects 4x faster than fentanyl...  (opioid Opioid An opioid is a psychoactive chemical that works by binding to opioid receptors, which are found principally in the central and peripheral nervous system and the gastrointestinal tract...  analgesic Analgesic An analgesic is any member of the group of drugs used to relieve pain . The word analgesic derives from Greek an- and algos .... ) methadone Methadone Methadone is a synthetic opioid, used medically as an analgesic and a maintenance anti-addictive for use in patients with opioid dependency. It was developed in Germany in 1937...  (anti-addictive) sorafenib Sorafenib Sorafenib , is a drug approved for the treatment of primary kidney cancer and advanced primary liver cancer ....  (protein kinase Protein kinase A protein kinase is a kinase enzyme that modifies other proteins by chemically adding phosphate groups to them . Phosphorylation usually results in a functional change of the target protein by changing enzyme activity, cellular location, or association with other proteins...  inhibitor)	Strong: Orphenadrine Orphenadrine Orphenadrine is an anticholinergic drug of the ethanolamine antihistamine class with prominent CNS and peripheral actions used to treat painful muscle spasms, other similar conditions, as well as the treatment...  (analgesic Analgesic An analgesic is any member of the group of drugs used to relieve pain . The word analgesic derives from Greek an- and algos .... ) Unspecified potency ticlopidine Ticlopidine Ticlopidine is an antiplatelet drug in the thienopyridine family. Like clopidogrel, it is an adenosine diphosphate receptor inhibitor. It is used in patients in whom aspirin is not tolerated, or in whom dual antiplatelet therapy is desirable...  (antiplatelet) ThioTEPA ThioTEPA N,N'N'-triethylenethiophosphoramide is an alkylating agent used to treat cancer.ThioTEPA is an organophosphorus compound with the formula SP3. It is an analogue of N,N',N- triethylenephosphoramide . This molecule features tetrahedral phosphorus and is structurally akin to phosphate...  (anticancer) Curcumin Curcumin Curcumin is the principal curcuminoid of the popular Indian spice turmeric, which is a member of the ginger family . The other two curcuminoids are desmethoxycurcumin and bis-desmethoxycurcumin. The curcuminoids are natural phenols and are responsible for the yellow color of turmeric...  (constituent of turmeric Turmeric Turmeric is a rhizomatous herbaceous perennial plant of the ginger family, Zingiberaceae. It is native to tropical South Asia and needs temperatures between 20 °C and 30 °C and a considerable amount of annual rainfall to thrive... )	rifampicin Rifampicin Rifampicin or rifampin is a bactericidal antibiotic drug of the rifamycin group. It is a semisynthetic compound derived from Amycolatopsis rifamycinica ...  (bactericidal) carbamazepine Carbamazepine Carbamazepine is an anticonvulsant and mood-stabilizing drug used primarily in the treatment of epilepsy and bipolar disorder, as well as trigeminal neuralgia...  (anticonvulsant Anticonvulsant The anticonvulsants are a diverse group of pharmaceuticals used in the treatment of epileptic seizures. Anticonvulsants are also increasingly being used in the treatment of bipolar disorder, since many seem to act as mood stabilizers, and in the treatment of neuropathic pain. The goal of an... , mood stabilizer Mood stabilizer A mood stabilizer is a psychiatric medication used to treat mood disorders characterized by intense and sustained mood shifts, typically bipolar disorder.-Uses:... ) phenobarbital Phenobarbital Phenobarbital or phenobarbitone is a barbiturate, first marketed as Luminal by Friedr. Bayer et comp. It is the most widely used anticonvulsant worldwide, and the oldest still commonly used. It also has sedative and hypnotic properties but, as with other barbiturates, has been superseded by the...  (anticonvulsant Anticonvulsant The anticonvulsants are a diverse group of pharmaceuticals used in the treatment of epileptic seizures. Anticonvulsants are also increasingly being used in the treatment of bipolar disorder, since many seem to act as mood stabilizers, and in the treatment of neuropathic pain. The goal of an...  ) phenytoin Phenytoin Phenytoin sodium is a commonly used antiepileptic. Phenytoin acts to suppress the abnormal brain activity seen in seizure by reducing electrical conductance among brain cells by stabilizing the inactive state of voltage-gated sodium channels...  (antiepileptic)