Effect of beta-carotene on the transformation of tyrosine by nitrogen dioxide and peroxynitrous acid

In the NO2-exposure of tyrosine in 70% dioxane/phosphate buffer (pH 7.4), b eta-carotene enhanced the degradation of tyrosine and/or 3-nitrotyrosine pr oduced, whereas alpha-tocopherol and ascorbyl palmitate inhibited the trans formation of tyrosine into 3-nitrotyrosine. Generation of certain active sp ecies in the interaction of beta-carotene with NO2 was suggested. Ascorbyl palmitate effectively and alpha-tocopherol slightly inhibited the transform ation of tyrosine in the NO2-exposure in the presence of beta-carotene. In the reaction of tyrosine with ONOO-/ONOOH, beta-carotene enhanced the degra dation of 3-nitrotyrosine produced suggesting generation of certain active species, whereas alpha-tocopherol and ascorbyl palmitate completely suppres sed the transformation of tyrosine into 3-nitrotyrosine.