Enzyme 'Bilirubin Reductase' Identified as Cause of Urine's Yellow Color

Discovery could lead to new insights into gut health and conditions like jaundice and inflammatory bowel disease

Scientists have identified the enzyme 'bilirubin reductase' as the cause of urine's yellow color, solving a long-standing mystery in biology.
The enzyme is produced by gut bacteria and is a result of the degradation of red blood cells, which produce a bright orange pigment called bilirubin.
Bilirubin is secreted into the gut where it is converted into a colorless byproduct called urobilinogen, which then degrades into a molecule called urobilin, responsible for the yellow color of urine.
The enzyme is present in almost all healthy adults but is often missing from newborns and individuals with inflammatory bowel disease, suggesting a potential link to conditions like jaundice and pigmented gallstones.
The discovery could pave the way for further research into the gut microbiome’s role in ailments like jaundice and inflammatory bowel disease.