A deficiency in which enzyme leads to the accumulation of bilirubin and causes jaundice?

A deficiency in glucuronyl transferase leads to the accumulation of bilirubin, which causes jaundice. Glucuronyl transferase is an enzyme crucial for the conjugation of bilirubin, enabling it to be more water-soluble and facilitating its excretion from the liver into bile. When there is insufficient activity of this enzyme, bilirubin cannot be effectively processed and eliminated from the body, leading to high levels in the bloodstream. This accumulation results in the yellowing of the skin and eyes known as jaundice.

The other enzymes listed do not directly participate in the conjugation process of bilirubin. Heme oxygenase plays a role in the breakdown of hemoglobin into bilirubin but does not contribute to its elimination. Glucuronidase acts on glycosaminoglycans and is not directly involved in bilirubin metabolism. Bilirubin reductase is responsible for reducing bilirubin but is less crucial in the context of conjugation and excretion pathways. Therefore, the deficiency in glucuronyl transferase specifically links to the inability to metabolize bilirubin, leading to jaundice.