Phase II biotransformations are detoxification mechanisms that conjugate xenobiotics with endogenous substances, neutralizing their toxicity.
A key example involves the conjugation of cyanide ions, which impair cellular respiration and alter hemoglobin into non-oxygen-carrying cyanmethemoglobin. To neutralize this threat, a sulfur atom from thiosulphate is transferred to the cyanide ion, catalyzed by the enzyme rhodanese, resulting in an inactive compound called thiocyanate. The production of thiosulfate occurs through the transamination of β-cysteine to mercaptopyruvate.
Another significant phase II reaction involves conjugating endogenous purine and pyrimidine bases with ribose to create nucleotides. These nucleotides play a crucial role in protein synthesis and energy metabolism, highlighting the importance of this biotransformation process.
Finally, taurine, a β-amino sulphonic acid, contributes significantly to bile production. It conjugates with endogenous bile acids, adding to the composition of bile, which plays a pivotal role in digestion.
Phase II conjugation reactions neutralize harmful substances, support essential biological processes, and contribute to digestive functions, demonstrating their importance in maintaining overall health.
From Chapter 5:
Now Playing
Pharmacokinetics: Drug Biotransformation
48 Views
Pharmacokinetics: Drug Biotransformation
399 Views
Pharmacokinetics: Drug Biotransformation
245 Views
Pharmacokinetics: Drug Biotransformation
150 Views
Pharmacokinetics: Drug Biotransformation
69 Views
Pharmacokinetics: Drug Biotransformation
182 Views
Pharmacokinetics: Drug Biotransformation
80 Views
Pharmacokinetics: Drug Biotransformation
167 Views
Pharmacokinetics: Drug Biotransformation
311 Views
Pharmacokinetics: Drug Biotransformation
182 Views
Pharmacokinetics: Drug Biotransformation
156 Views
Pharmacokinetics: Drug Biotransformation
191 Views
Pharmacokinetics: Drug Biotransformation
149 Views
Pharmacokinetics: Drug Biotransformation
193 Views
Pharmacokinetics: Drug Biotransformation
123 Views
Copyright © 2025 MyJoVE Corporation. All rights reserved