Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas, Departamento de Química, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, CCT La Plata-CONICET, Boulevard 113 y 64, 1900, La Plata, Argentina.
Biochem Biophys Res Commun. 2012 Aug 3;424(3):568-72. doi: 10.1016/j.bbrc.2012.06.155. Epub 2012 Jul 7.
Tyrosinase catalyzes in mammals the first and rate-limiting step in the biosynthesis of the melanin, the main pigment of the skin. Pterins, heterocyclic compounds able to photoinduce oxidation of DNA and its components, accumulate in the skin of patients suffering from vitiligo, a chronic depigmentation disorder in which the protection against UV radiation fails due to the lack of melanin. Aqueous solutions of tyrosinase were exposed to UV-A irradiation (350 nm) in the presence of pterin, the parent compound of oxidized pterins, under different experimental conditions. The enzyme activity in the irradiated solutions was determined by spectrophotometry and HPLC. In this work, we present data that demonstrate unequivocally that the enzyme is photoinactivated by pterin. The mechanism of the photosensitized process involves an electron transfer from tyrosinase to the triplet excited state of pterin, formed after UV-A excitation of pterin. The biological implications of the results are discussed.
酪氨酸酶在哺乳动物中催化黑色素生物合成的第一步和限速步骤，黑色素是皮肤的主要色素。蝶呤是一种能够光诱导 DNA 及其成分氧化的杂环化合物，在患有白癜风的患者的皮肤中积累，白癜风是一种慢性色素减退疾病，由于缺乏黑色素，导致对紫外线辐射的保护失败。在不同的实验条件下，将酪氨酸酶的水溶液暴露于 UV-A 辐射（350nm）下，并存在蝶呤，即氧化蝶呤的母体化合物。通过分光光度法和 HPLC 测定辐照溶液中的酶活性。在这项工作中，我们提供的数据无可置疑地证明了酶被蝶呤光失活。光敏化过程的机制涉及从酪氨酸酶到蝶呤的三重激发态的电子转移，该三重激发态在蝶呤的 UV-A 激发后形成。讨论了结果的生物学意义。
