Methionine oxidation and apoptosis induction by ascorbate, gallate and hydrogen peroxide

Addition of either ascorbate, gallate, caffeate or hydrogen peroxide to the culture medium stimulated the oxidation of free methionine to methionine sulfoxide, regardless of the presence or absence of the cells. In methionine-free medium, growth of human myelogenous leukemic cell lines was nearly stopped by G1 arrest, without induction of internucleosomal DNA cleavage. Methionine sulfoxide, a major oxidation product of methionine, was neither growth-promoting nor cytotoxic. On the other hand, methional, a deamination and decarboxylation product of methionine, was highly cytotoxic. The present study suggests that the apoptosis induction by these antioxidants and oxidant cannot simply be explained by methionine oxidation or depletion.