This video includes in short about biotransformation and microsomal enzyme prepared by Kartik Tiwari

1. Kartik Tiwari
● Outline-:
● Microsomal enzyme
● Microsomal enzyme induction
● Biotransformation
● Phase of biotransformation
● Organ involve in biotransformation
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2. Microsomal enzymes
These are located on smooth endoplasmic reticulum (a system of microtubules
inside the cell), primarily in liver, also in kidney, intestinal mucosa and lungs.
The monooxygenases, cytochrome P 450, glucuronyl transferase, etc. are
microsomal enzymes. They catalyse most of the oxidations, reductions,
hydrolysis and glucuronide conjugation. Microsomal enzymes are inducible by
drugs, diet and other agencies.
MICROSOMAL ENZYME INDUCTION
Many drugs, insecticides and carcinogens interact with DNA and increase the
synthesis of microsomal enzyme protein, specially cytochrome P-450 and
glucuronyl transferase. As a result rate of metabolism of inducing drug itself
and/or other drugs is increased.
Different inducers are relatively selective for certain cytochrome P-450 enzyme
families, e.g.:
• Anticonvulsants including phenobarbitone, rifampin, glucocorticoids induce
CYP3A isoenzymes.

3. • Phenobarbitone also induces CYP2B1 and rifampin also induces CYP2D6.
• Isoniazid and chronic alcohol consumption induce CYP2E1.
• Polycyclic hydrocarbons like 3-methylcholanthrene and benzopyrene found in
cigarette smoke, charcoalbroiled meat and industrial pollutants induce CYP1A
isoenzymes.
• Other important enzyme inducers are: chloral hydrate, phenylbutazone,
griseofulvin, DDT. Since different CYP isoenzymes are involved in the
metabolism of different drugs, every inducer
increases biotransformation of certain drugs but not that of others. However,
phenobarbitone like of CYP3A and CYP2D6 affect the metabolism of a large
number of drugs, because these isoenzymes act on many drugs. On the
other hand induction by polycyclic hydrocarbons is limited to few drugs (like
theophylline, phenacetin) because CYP1A isoenzyme metabolizes only few
drugs.

4. Induction involves microsomal enzymes in liver as well as other organs and
increases the rate of metabolism by 2–4 fold. Induction takes 4–14 days to
reach its peak and is maintained till. he inducing agent is being given.
Thereafter the enzymes return to their original value over 1–3 weeks.
Biotransformation
The processes by which biochemical reactions alter the
drugs/xenobiotics within the body
• Chemical alteration of the drugs in body
• Renders Non-polar(Lipid Soluble) compounds Polar (Lipid Insoluble)
• So that they are not reabsorbed & are excreted
Biotransformation of drugs may lead to the following-
A. Active drug Inactive metabolite
Eg. 1) Lidocaine
2) Ibuprofen
3) Chloramphenicol

5. 4) Propranolol
● Biotransformation of drugs may lead to the following

6. ● Biotransformation of drugs may lead to the following

7. Metabolism takes place in two steps which is Phase I and Phase ll
reaction which is depicted as above

8. Organs involve in metabolism