Photosensitization of Proteins and Peptides by Pterin

M. LAURA DÁNTOLA; CAROLINA LORENTE; ESTHER OLIVEROS; BEATRIZ N. ZURBANO; CAROLINA CASTAÑO; ANDRÉS H. THOMAS

Córdoba

Congreso; 16th International Congress on Photobiology; 2014

International Union of Photobiology

Solar radiation induces modifications to different biomolecules and is implicated in the generation of human skin cancers. In particular, UV-A radiation (320-400 nm) can induce damage to DNA and other macromolecules through photosensitized reactions. This indirect action may be mediated by endogenous or exogenous photosensitizers and can take place through different mechanisms.   Oxidized pterins, efficient photosensitizers under UV-A irradiation [1], accumulate in the skin of patients suffering from vitiligo, a chronic depigmentation disorder [2]. We have investigated the ability of pterin (Ptr), the parent compound of oxidized pterins, to photosensitize the oxidation of several substrates: proteins (albumin, tyrosinase), the peptide a-melanocyte-stimulating hormone and free amino acids (tryptophan (Trp), tyrosine (Tyr), etc). The mechanism of the photosensitized processes is initiated by an electron transfer from the substrate to the triplet excited stated of Ptr. The photosensitized process produces chemical changes in, at least, two different amino acid residues: Trp and Tyr. The present findings are analyzed in the context of the general behavior of pterins as photosensitizers and the biological implications are discussed.   Acknowledgments The authors thank the CNRS and CONICET financial support.   [[1]] G. Petroselli, M. L. Dántola, F. M. Cabrerizo, A. L. Capparelli, C. Lorente, E. Oliveros, A. H. Thomas, J. Am. Chem. Soc. 2008, 130, 3001. [2] K. U. Schallreuter, J. M. Wood, M. R. Pittelkow, M. Gutlich, K. R. Lemke, W. Rodl, N. N. Swanson, K. Hitzemann, I. Ziegler, Science, 1994, 263, 1444.