ACC synthase that is localized in the cytoplasm is a soluble enzyme
with a relative molecular mass of 50 kDa (kilodalton). ACC synthase has several isoforms
that are differentially expressed in response to wounding, other stress factors, and at the
initiation of ripening. In apple fruits, ACC oxidase was localized in the cytosol using immunoelectron
microscopy (Chung et al., 2002). Using molecular biology tools, a cDNA
(complementary DNA representing the coding sequences of a gene) for ACC oxidase was
isolated from tomato, which encodes a protein with a relative molecular mass of 35 kDa
(Hamilton et al., 1991).ACC-oxidase reaction occurs in the presence of Fe2+, ascorbate, and
oxygen.