Galactono-1,4-lactone oxidation, enzymic

It was also found that L-gulono-1,4-lactone (21) is enzymically oxidized to L-ascorbic acid (1) in 40% yield by using an enzyme system isolated from a variety of natural sources, including rat livers and germinating peas.378 L-Galactono- 1,4-lactone (16) was also oxidized to 1 with this enzyme system. 

Besides GLOs of animal species, the terminal enzymes of biosynthetic pathways of ascorbic acid in bakers yeast and in sweet potato were highly purified. Nishikimi et al. (1978) purified L-galactono-7-lactone oxidase from mitochondria of the yeast. This enzyme catalyzes the oxidation of L-galactono-7-lactone approximately three times as fast as that of L-gulono-7-lactone using O2 as the electron acceptor. Its molecular mass (monomer) was determined to be 56,000 daltons. Bleeg and Christensen (1982) also purified the enzyme from bakers yeast and... 

Confirmation that the synthesis of n-ascorbic acid m vwo does in fact proceed via these or very similar routes was obtained in work in which the enzymic oxidation in vitro of L-galactono-7-lactone to L-ascorbic acid by plant mitochondria was demonstrated (Mapson et al., 1954). The enzymes responsible were located entirely within the cytoplasmic particles (mitochondria), and their activity depended on the maintenance of the mitochondria in an intact condition. 

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