Ficz

Acronym for the indolocarbazole "6-formylindolo-carbazole", a photoproduct generated by photo-oxidation and resulting from the amino acid tryptophan (tryptone phadimer: dimer = molecule or a molecular compound consisting of two often identical subunits, the monomers). Tryptophan thus functions as a UV chromophore. FICZ is metabolized very quickly in the cytoplasm of cells. Thus, UV irradiation leads to a rapid increase of FICZ in keratinocytes, but also systemically (detectable in urine samples of UV-irradiated volunteers). FICZ has one of the strongest affinities to a cytoplasmic protein, the arylhydroxycarbon receptor (AhR). This protein triggers the internal signaling pathways in keratinocytes and melanocytes and also induces melanogenesis (see pigmentation below).

1. Brenner M et al (2010) Basics of skin pigmentation. Dermatologist 61: 554-560
2. Esser C et al (2010) UV radiation and pigmentation. dermatologist 61: 561-565
3. Fritsche E et al (2007): Lightening up the UV response: The AhR is a cytoplasmic photosensor. Proc Natl Acad Sci 104:8851-8856.