BilR (Bilirubin Reductase - the enzyme in bacteria that breaks down Bilirubin). The pathway is basically: Hemoglobin => Heme => Biliverdin => Bilirubin => Uro

BilR (Bilirubin Reductase - the enzyme in bacteria that breaks down Bilirubin). The pathway is basically: Hemoglobin => Heme => Biliverdin => Bilirubin => Urobilinogen => Urobilin The general pathway has been known for a while and basically got Hans Fischer the Nobel Prize for Chemistry in 1930. What was not known was the enzyme that converted Bilirubin to Urobilinogen. Previously we said it was just "bacteria."