Bilirubin conjugates glucuronides

In adults, virtually all bilirubin excreted in bile is in the form of glycosidic conjugates glucuronides account for 95% of them and glucosides and xylosides constitute the remainder. Of the glucuronides, diglucuronide is the major fraction ( 90%) and monoglucuronide the minor fraction (-10%). 

It is not clear if the absence of dehydrogenase and transferase activity in the newborn liver results from the reduced concentration of the enzyme or from the presence of inhibitors. Some experiments have shown that the sera of pregnant women and newborn infants contain substances that inhibit bilirubin conjugation in liver slices. An experiment in which the bilirubin glucuronide conjugation is determined when micro-somes from normal and newborn liver are mixed could reveal whether an inhibitor exists. 

Several bilirubin conjugates have been isolated from human hepatic bile as the phenylazo derivatives. The major bilirubin conjugates are excreted, not as was formerly thought in the form of glucuronides, but as the acyl glycosides of three aldobiouronic acids, one hexurono l-hexuronic acid, and one pseudoaldobiouronic acid. The conjugation of human metabolites with acidic disaccharides of the above types has not been reported previously. 

MRP2 (ABCC2) LTC4, bilirubin-glucuronide, estradiol 17 3-glucuronide, dianionic bile salts, anionic conjugates, glutathione disulfide, and others... 

Glucuronide synthesis is the rate-determining step in hepatic bilirubin metabolism. Drugs such as phenobarbital, for example, can induce both conjugate formation and the transport process. 

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