Photochemistry of 5-S-cysteinyldopa.
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.
Costantini
C
C
Department of Organic and Biological Chemistry, University of Naples, Italy.
d'Ischia
M
M
Palumbo
A
A
Prota
G
G
D003548:Cysteinyldopa / Q000737:chemistry* / Q000502:physiology; D010777:Photochemistry; D011789:Quantum Theory; D013056:Spectrophotometry, Ultraviolet; D014466:Ultraviolet Rays
D003548:Cysteinyldopa