They discover why urine is yellow after centuries of mystery

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Scientists Discover Enzyme Responsible for Yellow Color of Urine

Washington. For centuries, scientists have wondered why urine is yellow. Now a team of American researchers has discovered that the person responsible for the yellowish color is an enzyme called bilirubin reductase.

In a study published this Wednesday in Nature Microbiology, a team from the University of Maryland led by Professor Brantley Hall revealed the discovery of the enzyme.

“The discovery of this enzyme finally unravels the mystery of the yellow color of urine. It is incredible that an everyday biological phenomenon went unexplained for so long and our team is delighted to be able to explain it,” Hall said in a statement.

The University of Maryland team explained that when red blood cells break down after about six months of existence, a yellow-orange bile pigment called bilirubin is produced. In the intestine, microbes create the enzyme bilirubin reductase to convert bilirubin into a colorless compound called urobilinogen, which in turn spontaneously breaks down into a molecule called urobilin.

“Urobilin is ultimately responsible for the yellow color we all know,” Hall added.

But beyond answering a curiosity that has intrigued generations, the discovery of bilirubin reductase may also facilitate research into the role of the gut microbiome in diseases such as jaundice or intestinal inflammation.

When bilirubin, which is secreted in the intestine for subsequent excretion, is absorbed in excess into the bloodstream, it can cause jaundice, a disease that causes the eyes and skin to appear yellowish.

The team of researchers also discovered that although bilirubin reductase is present in almost all healthy adults, newborns and individuals with inflammatory bowel disease often lack this enzyme.

Another of the authors of the study, researcher Xiaofang Jiang, stated that after identifying the enzyme bilirubin reductase, we can begin to investigate how intestinal bacteria affect bilirubin levels and diseases such as jaundice.

In addition, the gut microbiome has also been linked to other diseases such as allergies, arthritis and psoriasis (a chronic inflammatory skin disease), so the impact of discovering the origin of the yellow color of urine may go beyond the simple anecdote.