Cis-Urocanic acid

Cis-Urocanic acid (cUCA) is a biochemical compound that plays a significant role in the metabolism of the amino acid histidine. It is a photoreceptor and a part of the skin's natural sun-screening mechanism.

Structure and Properties

Cis-Urocanic acid is a carboxylic acid with a pyrrole ring structure. It is the cis-isomer of Urocanic acid, which means it has a different spatial arrangement of atoms. The cis-isomer is less stable than the trans-isomer, and can be converted to the trans form by ultraviolet (UV) radiation.

Biological Role

Cis-Urocanic acid is a major component of the stratum corneum, the outermost layer of the epidermis. It is produced from histidine by the action of the enzyme histidase. In the skin, cUCA absorbs UV-B radiation and converts it to less harmful heat, thus protecting the underlying tissues from UV damage.

When the skin is exposed to UV radiation, cUCA is isomerized to trans-Urocanic acid (tUCA). This process triggers a cascade of biochemical reactions that lead to an increase in the production of melanin, the pigment that gives skin its color and protects it from UV radiation.

Health Implications

The conversion of cUCA to tUCA by UV radiation has been implicated in the development of skin cancer. Studies have shown that tUCA can suppress the immune response in the skin, allowing cancer cells to grow unchecked.

In addition, abnormal levels of cUCA have been found in the skin of patients with psoriasis, a chronic skin disease characterized by red, scaly patches. This suggests that cUCA may play a role in the pathogenesis of this condition.

See Also

• Histidine metabolism
• Urocanic acid
• Skin cancer
• Psoriasis