Page 154 - Interactive Theoritical Notes of Bioharmaceutics and pharamcokinetics.docx compressed

PharmD clinical pharmacy program Level 3, Semester 2 Biopharmaceutics & Pharmacokinetics (PT608(

Examples of non-microsomal enzymes having important roles in the metabolism of
endogenous and exogenous substances

 Alcohol- and aldehyde dehydrogenase;

 Xanthine oxidase;
 Tyrosine hydroxylase; and
 Monoamine oxidase.

2- Reduction

Reduction reactions (e.g., the addition of hydrogen or the removal of oxygen from the

parent molecule) occur both in microsomal and non-microsomal fractions of hepatic

and other cells. Examples of such reactions include nitro-, azo-, aldehyde-, ketone-,

and quinone reduction.

3- Hydrolysis

Hydrolysis-type reactions can occur in multiple locations throughout the body,

including the plasma. Examples of some nonmicrosomal hydrolases include esterases,

peptidases, and amidases.

Phase II Reactions (Conjugation reactions)

 Phase I reactions convert a drug to a more polar compound by introducing or

unmasking polar functional groups such as -OH, -NH2, or -SH.

 Some Phase I products are still not eliminated rapidly, and hence undergo Phase

II reactions involving conjugation of the newly established polar group with

endogenous compounds such as:

 Glucuronic acid,

 Sulfuric acid,

 Acetic acid, or

 Amino acids (typically glycine).

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