Urocanic acid isomerization

Urocanic acid isomerization" refers to the **conversion between the trans and cis forms of urocanic acid**, a naturally occurring metabolite found predominantly in the stratum corneum of human skin. The most biologically relevant process is the **photoisomerization** from trans‑urocanic acid to cis‑urocanic acid upon exposure to ultraviolet B (UVB) radiation. This reaction does not refer to a specific protein, receptor, or drug target but rather describes a chemical transformation that can occur spontaneously under UV light or be catalyzed by certain microbial enzymes such as *cis*-UCA isomerase in some bacteria[3][6]. Trans‑urocanic acid acts as an endogenous sunscreen, absorbing UVB and protecting against DNA damage; its photoisomerized product, *cis*-urocanic acid, has been shown to activate regulatory T cells and contribute to immunosuppression following sun exposure[1][3]. The balance between these two forms may influence susceptibility to immune-mediated skin conditions. In clinical biochemistry, measurement of this ratio serves as a sensitive indicator for suberythemal UVB doses and sunscreen efficacy assessment[1]. Because "Urocanic acid isomerization" describes a **chemical process** rather than an individual molecular target such as an enzyme or receptor, it should not be considered a therapeutic target itself. Instead, enzymes involved in its metabolism—such as histidine ammonia lyase or microbial *cis*-UCA isomerases—are more appropriate molecular targets if relevant for research purposes[2][3][6].

Other names

Urocanic acid photoisomerizationtrans-urocanic acid to cis-urocanic acid conversioncis-trans urocanic acid isomerization