Production of 1,5-anhydroglucitol from 1,5-anhydrofructose in erythroleukemia cells

The pyranoid polyol 1,5-anhydroglucitol (1,5AnGlc-ol) occurs in a wide variety of organisms. Tn humans, it is present as one of the major monosaccharide components in body fluids and serves as an indicator for glycemic control in diabetic care. However, its metabolic origin and fate have been poorly understood. Here we demonstrate that 1,5AnGlc-ol is produced from glucose in erythroleukemia cells, K-562. We show the occurrence of 1,5-anhydrofructose (1,5AnFru), a derivative of 1,5AnGlc-ol oxidized at the C2 position, in K-562 cells. In addition, several pieces of evidence indicated that 1,5AnFru, rather than glucose, was the immediate precursor in 1,5AnGlc-ol production in erythroleukemia cells: exogenous 1,5AnFru was readily taken up into the cells and reduced to 1,5AnGlc-ol, but the reverse reaction, oxidation of 1,5AnGlc-ol to 1,5AnFru, was scarcely observed. The apparent K-m of the overall cellular reduction for 1,5AnFru was estimated as 70 mg/l. This reduction was markedly inhibited by glucose in the culture medium but not by 1,5AnGlc-ol or glucitol. Since 1,5AnFru arises from alpha-1,4-glucans through lyase reactions in fungi and algae, we suggest the possibilities that glycogen is the precursor of 1,5AnFru and, therefore, 1,5AnGlc-ol originates from glycogen in mammals.