Bilirubin, the degradation product of heme, is only mildly water-soluble. The solubility of bilirubin in water is increased by forming a conjugate with which of the following?

Question

Quizplus · Accepted Answer

Bilirubin becomes more water-soluble when it is conjugated with glucuronic acid in the liver, forming bilirubin diglucuronide, which is more easily excreted in bile.  In hepatocytes, bilirubin-UDP-glucuronyltransferase (bilirubin-UGT) adds 2 equivalents of glucuronic acid to bilirubin to produce the more water-soluble, bilirubin diglucuronide derivative. The increased water solubility of the tetrapyrrole facilitates its excretion with the remainder of the bile as the bile pigments.

Bilirubin, the Degradation Product of Heme, Is Only Mildly Water-Soluble