Phase II Reactions: Miscellaneous Conjugation Reactions

Phase II biotransformations primarily involve detoxification processes where xenobiotics conjugate with endogenous substances.

The cyanide ion's toxicity stems from its capacity to inhibit vital cellular respiration enzymes and transform hemoglobin into cyanomethemoglobin, which cannot deliver oxygen to tissues.

The body neutralizes cyanide ions via conjugation. In this process, a sulfur atom from thiosulphate is transferred to the cyanide ion in the presence of the enzyme rhodanese, forming an inactive thiocyanate.

Thiosulfate is produced via a biochemical process where β-cysteine is transaminated to mercaptopyruvate.

Another phase II conjugation involves endogenous purine and pyrimidine bases conjugating with ribose, forming nucleotides. This process is vital for essential biological functions like protein synthesis and energy metabolism.

Lastly, taurine, a β-amino sulphonic acid, plays a pivotal role in bile production. It conjugates with endogenous bile acids, contributing to the composition of bile, a crucial element in digestion.