Xenobiotic metabolism
Xenobiotic metabolism is the set of metabolic pathways that modify the chemical structure of xenobiotics, which are compounds foreign to an organism's normal biochemistry, such as drugs and poisons. These pathways are a form of biotransformation present in all major groups of organisms, and are considered to be of ancient origin. These reactions often act to detoxify poisonous compounds (although in some cases, bioactivation is possible).
Overview[edit | edit source]
Xenobiotics are compounds that are foreign to a living organism. They include substances like drugs, environmental pollutants, and natural compounds from plants and microorganisms. The body has developed various mechanisms to eliminate these substances, and xenobiotic metabolism is one of them.
Phases of Xenobiotic Metabolism[edit | edit source]
Xenobiotic metabolism typically consists of three phases: Phase I reactions, Phase II reactions, and Phase III reactions.
Phase I Reactions[edit | edit source]
Phase I reactions (also termed nonsynthetic reactions) may occur by oxidation, reduction, hydrolysis, cyclization, and decyclization reactions. Oxidation involves the enzymatic addition of oxygen or removal of hydrogen, carried out by mixed function oxidases, often in the liver.
Phase II Reactions[edit | edit source]
Phase II reactions (also termed conjugation reactions) involve the enzymatic conjugation of endogenous compounds, such as glucuronic acid or sulfate, to the xenobiotic.
Phase III Reactions[edit | edit source]
Phase III reactions involve the further modification of the xenobiotic-conjugate to increase its water solubility for excretion.
Enzymes Involved[edit | edit source]
The enzymes involved in xenobiotic metabolism are primarily located in the liver, but can also be found in other parts of the body. The most important of these enzymes are the cytochrome P450 enzymes, which are responsible for the oxidation of xenobiotics.
Clinical Significance[edit | edit source]
Understanding xenobiotic metabolism is important in pharmacology and toxicology, as it can influence the efficacy and toxicity of drugs and other xenobiotics.
See Also[edit | edit source]
References[edit | edit source]
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