Kynurenine Unit Converter

Kynurenine is the first stable breakdown product of the essential amino acid tryptophan. Over 95% of dietary tryptophan is metabolized through the kynurenine pathway rather than being converted to serotonin, making kynurenine a central molecule in tryptophan metabolism.

Kynurenine sits at a critical branch point. It can be converted into neuroprotective kynurenic acid or into neurotoxic quinolinic acid, depending on which enzymes are most active. The balance between these two branches has important implications for brain health and immune function.

As a biomarker, kynurenine reflects the degree of tryptophan catabolism in the body. Elevated levels typically signal increased activity of the enzymes that initiate the pathway, most commonly driven by inflammation.

Kynurenine is produced when tryptophan is broken down by two key enzymes: TDO (tryptophan 2,3-dioxygenase), which is active mainly in the liver under normal conditions, and IDO1 (indoleamine 2,3-dioxygenase 1), which is expressed in immune cells, lungs, intestine, placenta, and brain and is strongly activated by inflammatory signals such as interferon-gamma.