The oxidation of phosphorylated and non-phosphorylated sugars by mammalian liver.

In 1928 Miiller (1) reported the presence of a new enzyme, a glucose oxidase, in press-juice of Aspergillus niger. He subsequently suggested that it might be a dehydrogenase (2) ; he later showed that it catalyzed the oxidation of glucose to gluconic acid (3). Harrison in 1931 obtained glucose dehydrogenase from acetone-dried mammalian liver by saturating a water extract with ammonium sulfate (4). The product of the oxidation was shown to be gluconic acid (5) and the cytochrome system a hydrogen carrier (6). Mtiller then resumed his work with glucose dehydrogenase and demonstrated the decolorization of methylene blue in the presence of a catalytic enzyme preparation from ox liver when galactose and xylose were present as substrates (7). Breusch (8) has more recently reported the existence of a D-arabinose dehydrogenase, a glyceraldehyde dehydrogenase, and a glycoaldehyde dehydrogenase in cat liver, and the probable existence of a n-erythrose dehydrogenase in the same tissue. Several dehydrogenases attacking phosphorylated derivatives of hexoses have been reported. Warburg and Christian (9) found an enzyme in erythrocytes that oxidizes glucose-6-phosphate when methylene blue is the carrier. The name Zwischenjerment was given by them (10) to the same or a similar hexose monophosphate dehydrogenase obtained from yeast which oxidizes glucose-8phosphate to phosphogluconic acid. Harrison (11) has indicated the presence of a hexose diphosphate dehydrogenase in muscle and liver which operates in the presence of methylene blue. The experiments reported herein verify the existence of enzymes in lamb liver that are capable of oxidizing n-glucose, D-arabinose, n-xylose, n-lyxose, n-glucose-6-phosphate, fructose-6-phosphate, and fructose-l,&phosphate when methylene blue and diphosphoand triphosphopyridine nucleotide are added to a partially purified preparation.