title: Photochemistry of 5-S-cysteinyldopa.
abstract: The photochemical behavior of 5-S-cysteinyldopa (5-S-CD), a colorless product of melanocyte metabolism, was investigated in neutral phosphate buffer with biologically relevant UV radiation. Exposure of 5-S-CD to pyrex-filtered UV light (wavelengths > 320 nm) was found to induce an oxygen-dependent reaction, leading to, besides abundant polymeric materials, the benzothiazine derivatives I and II (two diastereoisomers). Superoxide dismutase exerted a small inhibitory effect on 5-S-CD consumption, whereas other active oxygen scavengers had no effect on the reaction course. Addition of glutathione as a hydrogen donor completely suppressed the reaction. With UVB light (wavelength range 280-320 nm) photolysis of 5-S-CD proceeded mainly with formation of 3,4-dihydroxyphenylalanine, arising presumably by photohomolytic cleavage of the S-CH2 bond followed by desulfuration. These results are of interest in relation to the high susceptibility of fair-complexioned individuals to actinic damage and skin cancer.
authors.affiliation: Department of Organic and Biological Chemistry, University of Naples, Italy.
authors.forename: C
authors.initials: C
authors.lastname: Costantini
authors.forename: M
authors.initials: M
authors.lastname: d'Ischia
authors.forename: A
authors.initials: A
authors.lastname: Palumbo
authors.forename: G
authors.initials: G
authors.lastname: Prota
mesh_terms: D003548:Cysteinyldopa / Q000737:chemistry* / Q000502:physiology; D010777:Photochemistry; D011789:Quantum Theory; D013056:Spectrophotometry, Ultraviolet; D014466:Ultraviolet Rays
chemical_list: D003548:Cysteinyldopa