The enzyme that makes urine yellow has been finally identified. It has been known for more than 125 years that a compound called urobilin is responsible for urine’s yellow colour. But it was unclear how exactly it is created from the red-orange bilirubin.
“It’s remarkable that an everyday biological phenomenon went unexplained for so long, and our team is excited to be able to explain it,” Brantley Hall, an assistant professor in the University of Maryland’s Department of Cell Biology and Molecular Genetics, said in a news statement.
This waste product from degraded red blood cells can lead to jaundice and neurological damage if too much of it builds up in the body.
The enzyme, bilirubin reductase, is made by gut microbes and converts bilirubin into colourless urobilinogen, which breaks down further into yellow urobilin.
“Gut microbes encode the enzyme bilirubin reductase that converts bilirubin into a colorless byproduct called urobilinogen,” Hall, the study’s lead author, said. “Urobilinogen then spontaneously degrades into a molecule called urobilin, which is responsible for the yellow color we are all familiar with.”
The study authors said that before their research, scientists thought there were multiple enzymes involved, rather than a single enzyme.
