The biological oxidation of sorbitol.

Sorbitol is fermented in good yields to sorbose by some of the members of the Acetobacter species (1, 2). Resting cells of Acetobacter suboxydans may, in the absence of a source of nitrogen, oxidize sorbitol with the consumption of over 4 atoms of oxygen per molecule of substrate (3, 4). From a study of dinitrophenol action on this organism, the first step in sorbitol oxidation was shown to be non-phosphorylative (4, 5). Recently, a cyclic mechanism, the Horecker pentose cycle, has been demonstrated in A. suboxydans which can oxidize sugars to COz and water and can also lead to the formation of cellular materials (6). The present paper will demonstrate dual pathways for the oxidation of sorbitol by soluble extracts of A. suboxydans. In the presence of triphosphopyridine nucleotide (TPN), sorbose is formed; in the presence of diphosphopyridine nucleotide (DPN), fructose is produced.’ The fructose can then be phosphorylated and oxidized via the pentose cycle. Details of the properties of these TPNand DPN-linked dehydrogenases will be given in a later paper.