摘要
Most of the enzymatic reactions of ascorbate biosynthesis occur in the cytosol, with the exception of the terminal step, catalyzed by L-galactono-l,4-1actone dehydrogenase, which is localized on the inner mitochondrial membrane. Given the location of L-galactono-l,4-1actone dehydrogenase, the rate of ascorbate biosynthesis is intimately associated with the rate of mitochon- drial respiration （Nunes-Nesi et al., 2005）. Ascorbate has legion roles in the plant cell including mitosis, cell division, expansion and cell wall hydroxylation, hormone biosynthesis, signal transduction, programmed cell death, as well as protection against environmental stresses via detoxification of reactive oxygen species and regeneration of other antioxidants. This list has recently expanded with the epigenetic role exerted as a cofactor for DNA and histone demethylases in the nucleus and ascorbate may also be implicated in iron uptake （Pick and Weber, 2014）.
Most of the enzymatic reactions of ascorbate biosynthesis occur in the cytosol, with the exception of the terminal step, catalyzed by L-galactono-l,4-1actone dehydrogenase, which is localized on the inner mitochondrial membrane. Given the location of L-galactono-l,4-1actone dehydrogenase, the rate of ascorbate biosynthesis is intimately associated with the rate of mitochon- drial respiration （Nunes-Nesi et al., 2005）. Ascorbate has legion roles in the plant cell including mitosis, cell division, expansion and cell wall hydroxylation, hormone biosynthesis, signal transduction, programmed cell death, as well as protection against environmental stresses via detoxification of reactive oxygen species and regeneration of other antioxidants. This list has recently expanded with the epigenetic role exerted as a cofactor for DNA and histone demethylases in the nucleus and ascorbate may also be implicated in iron uptake （Pick and Weber, 2014）.
