Asked by: Natasa Ottemeyer
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Last Updated: 6th May 2024
What is the major role of Phase II biotransformation?
Transferases are the main phase II drug metabolizing enzymes. CONCLUSIONS: Phase II drugs metabolizing enzymes play a significant role in biotransformation and xenobiotics into more easily excretable forms, as well as the metabolic inactivation pharmacologically active substances.
What is involved in biotransformation Phases I and II?
The phase I reactions can be oxidation, reduction or hydrolysis. Phase II reactions are the conjugation or modification of chemicals with an endogenous moiety such as glucuronic acid (Williams 1959).
What is biotransformation and how does it work? Biotransformation is the chemical alteration or addition of chemicals to produce nutrients, amino acids, drugs, or toxins. Non-polar compounds must also be made polar to prevent them from being absorbed into the renal tubules. They are then excreted.
What is phase II metabolism, other than this?
The chemical changes that occur in phase 2 metabolism are those that alter the drug or its phase 1 metabolites. compounds that can be easily excreted from the urine. These reactions result in the formation of the molecule. O. OH.
Is there a place where the majority of Phase 2 biotransformation takes place?
Phase II metabolism is the addition of a hydrophilic, endogenous species such as glucuronic or sulfate to the drug molecule. Except for the microsomal enzyme glucuronidation enzyme which is involved in phase II reactions, enzymes are mostly located in the cell cytosol.
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What is the process of biotransformation?
Biotransformation is a process by which organic compounds are transformed from one form to another to reduce the persistence and toxicity of the chemical compounds. This process is aided by major range of microorganisms and their products such as bacteria, fungi and enzymes.
What are the four stages of drug metabolization?
The four stages are absorption, distribution, metabolism, and excretion. The entire process is sometimes abbreviated ADME.
What is the difference between Phase 1 and Phase 2 metabolism?
Phase II reactions are conjugation reactions where a molecule normally present in the body is added to the reactive site of the Phase I metabolite . The result is a conjugated metabolite that is more water soluble than the original xenobiotic or Phase I metabolite .
Where does Phase 2 metabolism occur?
Phase II reactions occur in the cytoplasm and commonly involve conjugation with sulphates, glucuronides, glutathione or amino acids and result in the formation of metabolites that are usually less toxic and more easily excreted.
What are the different types of biotransformation reaction?
Types of biotransformation reactions. Different types of chemical reactions occur during biotransformations, such as oxidation, reduction, hydrolysis, condensation, isomerization, formation of new C–C bonds, production of chiral compounds and reversal of hydrolytic reactions.
What is the difference between metabolism and biotransformation?
Biotransformation refers to alteration of a chemical by a biological system. It includes microbial action, but excludes (for example) photodegradation. Metabolism is often used as a synonym for biotransformation, but this is not strictly accurate. Metabolism is a somewhat narrower term.
Where does biotransformation occur in the body?
Drug biotransformation or metabolism principally occurs in the liver, kidney, skin, and GI tract.
What is a Phase 1 reaction?
Phase I reactions (also termed nonsynthetic reactions) may occur by oxidation, reduction, hydrolysis, cyclization, decyclization, and addition of oxygen or removal of hydrogen, carried out by mixed function oxidases, often in the liver.
What are the factors that affect metabolism?
Here are ten factors that affect BMR and metabolism:
- Here are ten factors that affect BMR and metabolism:
- Muscle mass. The amount of muscle tissue on your body.
- Age. As you get older, your metabolic rate generally slows.
- Body size.
- Gender.
- Genetics.
- Physical activity.
- Hormonal factors.
Why are drugs conjugated in Phase 2 metabolism?
Conjugation. Glucuronidation, the most common phase II reaction, is the only one that occurs in the liver microsomal enzyme system. Glucuronides are secreted in bile and eliminated in urine. Thus, conjugation makes most drugs more soluble and easily excreted by the kidneys.
What is Phase 1 biotransformation?
Phase I biotransformation reactions introduce or expose functional groups on the drug with the goal of increasing the polarity of the compound. Typically, oxidation is the most common phase I reaction. The hepatic cytochrome P450 system is the most important of the phase I oxidation systems (Figure 1).
What are the 3 phases of drug action?
A tablet or capsule taken by mouth goes through three phases—pharmaceutic, pharmacokinetic, and pharmacodynamic—as drug actions occur. In the pharmaceutic phase, the drug becomes a solution so that it can cross the biologic membrane.
What is Glucuronidation metabolism?
Glucuronidation consists of transfer of the glucuronic acid component of uridine diphosphate glucuronic acid to a substrate by any of several types of UDP-glucuronosyltransferase. The conjugation of xenobiotic molecules with hydrophilic molecular species such as glucuronic acid is known as phase II metabolism.
How does age affect drug metabolism?
Usually, age does not greatly affect clearance of drugs that are metabolized by conjugation and glucuronidation (phase II reactions). First-pass metabolism (metabolism, typically hepatic, that occurs before a drug reaches systemic circulation) is also affected by aging, decreasing by about 1%/yr after age 40.
What is cytochrome p450?
Cytochromes P450 (CYPs) are a superfamily of enzymes containing heme as a cofactor that function as monooxygenases. In mammals, these proteins oxidize steroids, fatty acids, and xenobiotics, and are important for the clearance of various compounds, as well as for hormone synthesis and breakdown.
Why are prodrugs used?
Prodrugs can be used to improve drug delivery or pharmacokinetics, to decrease toxicity, or to target the drug to specific cells or tissues. Ester and phosphate hydrolysis are widely used in prodrug design because of their simplicity, but such approaches are relatively ineffective for targeting drugs to specific sites.
What are drug metabolizing enzymes?
Drug-metabolizing enzymes are called mixed-function oxidase or monooxygenase and containing many enzymes including cytochrome P450, cytochrome b5, and NADPH-cytochrome P450 reductase and other components. Likewise, Cyp 1A2 activates a variety of bladder carcinogens, such as aromatic amines and amides.
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