Page 326 - Color Atlas of Biochemistry

Liver 317

A. Biotransformations

Acetic acid
H 2 O CH 3 -COOH

Foreign Endogenous O
substances: substances
C 1
Drugs Steroid hormones O CH 3 OH
Preservatives and other low COO COO
Plasticizers molecular weight
Pigments substances Acetylsalicylic acid Salicylate
Pesticides etc. Bile pigments
1. Hydrolysis of a drug
Poorly
soluble,
biologically
active, some S-adenosyl S-adenosyl homocysteine
toxic methionine
H N CH H N CH
Substrate Transformation 3 2 3 2
induction Phase I reactions: HO CH HO CH
reactions
Hydrolytic 2
cleavage,
Epoxide formation
Dealkylation OH OCH
Deamination 3
Reduction OH OH
Methylation
Desulfuration Norepinephrine O-methyl
norepinephrine
2. Methylation
of a hormone/neurotransmitter

Transformation Tetrahydrocortisol CH OH
2
product
CO
HO OH

Conjugate
formation:
Glucuronidation HO
Phase II Esterification H
Substrate reactions with sulfate
induction Amidation UDP-GlcUA
with Gly and Glu
3 CH OH
2
CO
UDP
HO OH
COO
H O H
H
Water soluble, OH H
Conjugate inactive,
non-toxic HO O H
H OH
Tetrahydrocortisol glucuronide

3. Glucuronidation of a hormone

Arylesterase Catechol O-methyl-
1 2
Bile Urine 3.1.1.2 transferase 2.1.1.6

3 Glucuronosyltransferase 2.4.1.17

Koolman, Color Atlas of Biochemistry, 2nd edition © 2005 Thieme
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