Kynurenic

Kynurenic acid (KYNA) is a product of the normal metabolism of amino acid L-tryptophan. It has been shown to act as an antiexcitotoxic and anticonvulsant, possibly by acting as a broad-spectrum antagonist at excitatory amino acid receptors. Because of these properties, it may have therapeutic applications.

Metabolism

KYNA is synthesized enzymatically from L-kynurenine, a metabolite of L-tryptophan, by the enzyme kynurenine aminotransferase. It is metabolized primarily in the liver and, to a lesser extent, in the brain.

Function

KYNA acts as a broad-spectrum antagonist at excitatory amino acid receptors, blocking the action of excitatory amino acids such as glutamate and aspartate. It also inhibits the α7 nicotinic acetylcholine receptor and the glycine site of the NMDA receptor. In addition, it has been shown to inhibit the reuptake of glutamate, thereby increasing the concentration of this neurotransmitter in the synaptic cleft.

Clinical significance

Elevated levels of KYNA have been found in the brains of individuals with schizophrenia and in the urine of patients with mania. It has been suggested that these elevated levels may contribute to the cognitive deficits seen in these conditions. Conversely, decreased levels of KYNA have been associated with depression and anxiety disorders.

See also

• Tryptophan
• Kynurenine pathway
• Schizophrenia
• Depression
• Anxiety disorders

References

Kynurenic Resources
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