Here I have described the CYP450 microsomal enzyme. A brief description is given. It will be very much helpful for UG & PG students.

1. MAULANA ABUL KALAM AZAD UNIVERSITY OF TECHNOLOGY, W.B.
DEPARTMENT OF PHARMACEUTICAL TECHNOLOGY
TOPIC : THE ENZYME CYTOCHROME P450
PRESENTED BY: SNEHASIS JANA
DIVISION: PHARMACOLOGY

2.  CONTENT:
•Introduction
•Nomenclature of CYP 450
•Why CYP called microsomal enzyme?
•Pharmacogenetics variation of CYP 450
•Major types of CYP450 enzymes
•Function of CYP450
•Enzyme inducers and inhibitors
•Conclusion

3.  INTRODUCTION
The Cytochrome P450 super family is a large and diverse group of enzyme,
contain active iron center.
In human body it is distributed throughout the body, maximum
concentration in Mitochondria, ER of human liver.
It has 44 subfamilies & more than 50 isoform.
75% of the total number of different
metabolic/bioactivation reaction are occur
by CYP450.
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Date- 15/12/2022 Time- 21:12:40 IST

4.  Nomenclature
Cyto- They are bound to the membrane of cells
Chrome P- Contain heme pigment.
The CYP 450 absorb light at wavelength at 450 nm
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Date- 15/12/2022 Time- 21:15:30 IST

5.  Why this CYP called as Microsomal Enzyme?
Microsome are derived from the endoplasmic reticulum. As this CYP450 is mostly
found in endoplasmic reticulum, it named as the microsomal enzyme.
 The Pharmacogenetics variation of CYP 450 enzyme:
• The CYP450 has pharmacogenetics variation.
• Different isoform of CYP450 are presents in different concentration in different persons.
• CYP2D6 has highly pharmacogenetics variation.
• Drugs that are metabolized by CYP2D6 will be different in person to person, the therapeutic
dose of such drug will be vary in different patients.

6. CYP 3A4 Forms the maximum hepatic content(26%) of CYP enzyme and is also involved in
metabolism of maximum percentage of drugs (33%).
CYP 2D6 content only 2% of total hepatic CYP content but involved in 23% of metabolic
function.
6 major CYP450 enzymes are CYP 3A4, CYP2D6, CYP 2C9, CYP 2C19, CYP 1A2, CYP 2E1
 Major CYP450 Enzymes

7.  Function of CYP450
I. Drug metabolism or biotransformation.
II. Making the drug molecule more polar by adding functional group.
III.Only have role in Phase-I detoxification reaction. (All the phase –II reactions are non
CYP mediated) As in phase-II reaction the microsomal reaction is only Glucoronide
conjugation reaction, which is non CYP mediated.
IV.This enzyme also involved in the metabolism of endogenous substances like bile acid
formation, cholesterol metabolism.

8. Only microsomal enzyme can be induced or inhibited by another substances. For example-
Enzyme inducers: will increase the number of microsomal enzyme, thus the metabolism of other
drug by the enzyme will also increase. Therefore dose of such drug should be increased when
administered along with enzyme inducers.
Some enzyme inducers are- Phenytoin, Rifampicin, Carbamazepine, Phenobarbitone, Smoking.
For example: A patient having the habits of regular smoking, and prescribed Theophyline for the
treatment of his bronchial asthma. As smoking is a enzyme inducers the Theophyline will easily
metabolized by this enzyme, so a higher dose of Theophyline is required for this patients than a
normal person.
 Enzymes Inducers and Inhibitors

9. Enzyme inhibitors: will decrease the number of microsomal enzyme, thus the metabolism of
other drug by the enzyme will also decrease. Therefore dose of such drug should be decreased
when administered along with enzyme inducers, otherwise it leads to toxicity.
Some enzyme inhibitors are- Ketoconazole, Cimetidine,Ciprofloxacin, Erythromycin, INH
For example: A patient is taking Theophyline for the treatment of bronchial asthma. But now he
got respiratory track infection and taking Ciprofloxacin for the treatment of his respiratory track
infection. As Ciproflixacin is an enzyme inhibitors it reduce the metabolism of Theophyline, so
the dose of Theophyline should be maintain according to that otherwise, it may cause the
Theophyline toxicity.
(Continued)

10. CONCLUSION
•CYP450 is a hemeprotein that’s play a key role in the metabolism of drug and others xenibiotics. Understanding
the CYP 450 system is essential for advanced research based on drug metabolism, drug-drug interaction.
•As it has genetic variation so the study of such enzyme is differ from every person to person and create different
pharmacological action.
•The enzyme inhibition and inducing property man be used in different therapeutic study based on these enzyme

11. References:
•Cook DJ, Finnigan JD, Cook K, Black GW, Charnock SJ. Cytochromes P450: history, classes, catalytic mechanism,
and industrial application. Advances in protein chemistry and structural biology. 2016 Jan 1;105:105-26.
•Manikandan P, Nagini S. Cytochrome P450 structure, function and clinical significance: a review. Current drug
targets. 2018 Jan 1;19(1):38-54.
•Katzung B.G, Trevor A.J.Drug Biotransformation. In:Katzung B.G,Trevor A.J, editors. Basic & Clinical
Phaemacology. 13th ed.India.McGraw Hill Education (India) Private Limited;2015. p. 56-63
•https://www.sciencedirect.com/topics/chemistry/cytochrome-p450

13. Questions ?