the ATP to ADP (Fig. 16.7). The ABC carriers including the GS-X pump named
multidrug resistance-associated protein 1 (MRP1) (Fig. 16.6) and P-gp (Ishikawa
1992; Hediger et al. 2004).
16.4 Types of Biotransformation
16.4.1 Enzymatic Elimination
The use of different metabolizing enzymes of the body/cells for the process of
biotransformation is known as enzymatic elimination. On the basis of compartmentalization of enzymes, it is broadly classified into non-microsomal biotransformation
and microsomal biotransformation (Smitha et al. 2017).
16.4.2 Non-microsomal Biotransformation
A type of biotransformation in which the concerned enzymes are soluble and are
present in the cytoplasm and mitochondria of cells in tissues including liver,
intestine, plasma, etc. (Gaynes and Fiscella 1996). These enzymes catalyze mainly
reductive and hydrolytic reactions, a few oxidative, and also conjugation reaction
except glucuronidation. This category contains alcohol dehydrogenase, aldehyde
dehydrogenase, monoamine oxidase, diamine oxidase, etc. (Gaynes and Fiscella
1996). The examples of reactions catalyzed by these enzymes include:
• Non-microsomal metabolism of catecholamines and noradrenaline via monoamine oxidase.
• Metabolism of ethanol into acetaldehyde by alcohol dehydrogenase.
As these enzymes are present in less quantity or a few are completely absent in
neonates, they make neonates sensitive to a few drugs. For example, even though
some drugs or syrups contain very less quantity of alcohol, they are still harmful to
children as they cannot metabolize the drug completely (Sellers and Holloway
1978).
16.4.3 Microsomal Biotransformation
A type of biotransformation in which enzymes responsible are present within the
lipophilic vesicle called microsome (Buhler and Williams 1988). These heterogeneous vesicles are formed from the endoplasmic reticulum when the cells are
disrupted in vitro. These range from 20 to 200 nm in diameter and are isolated by
differential centrifugation. They possess all functional, morphological properties of
the endoplasmic reticulum. These have mainly three structural features: rough
vesicles, smooth vesicles, and ribosomes & enzymes associated with it. In general,
16 Biotransformation: Basics and Applied Perspectives
347
multidrug resistance-associated protein 1 (MRP1) (Fig. 16.6) and P-gp (Ishikawa
1992; Hediger et al. 2004).
16.4 Types of Biotransformation
16.4.1 Enzymatic Elimination
The use of different metabolizing enzymes of the body/cells for the process of
biotransformation is known as enzymatic elimination. On the basis of compartmentalization of enzymes, it is broadly classified into non-microsomal biotransformation
and microsomal biotransformation (Smitha et al. 2017).
16.4.2 Non-microsomal Biotransformation
A type of biotransformation in which the concerned enzymes are soluble and are
present in the cytoplasm and mitochondria of cells in tissues including liver,
intestine, plasma, etc. (Gaynes and Fiscella 1996). These enzymes catalyze mainly
reductive and hydrolytic reactions, a few oxidative, and also conjugation reaction
except glucuronidation. This category contains alcohol dehydrogenase, aldehyde
dehydrogenase, monoamine oxidase, diamine oxidase, etc. (Gaynes and Fiscella
1996). The examples of reactions catalyzed by these enzymes include:
• Non-microsomal metabolism of catecholamines and noradrenaline via monoamine oxidase.
• Metabolism of ethanol into acetaldehyde by alcohol dehydrogenase.
As these enzymes are present in less quantity or a few are completely absent in
neonates, they make neonates sensitive to a few drugs. For example, even though
some drugs or syrups contain very less quantity of alcohol, they are still harmful to
children as they cannot metabolize the drug completely (Sellers and Holloway
1978).
16.4.3 Microsomal Biotransformation
A type of biotransformation in which enzymes responsible are present within the
lipophilic vesicle called microsome (Buhler and Williams 1988). These heterogeneous vesicles are formed from the endoplasmic reticulum when the cells are
disrupted in vitro. These range from 20 to 200 nm in diameter and are isolated by
differential centrifugation. They possess all functional, morphological properties of
the endoplasmic reticulum. These have mainly three structural features: rough
vesicles, smooth vesicles, and ribosomes & enzymes associated with it. In general,
16 Biotransformation: Basics and Applied Perspectives
347