HEPATIC PRODUCTION OF 1,5-ANHYDROFRUCTOSE AND 1,5-ANHYDROGLUCITOL IN RAT BY THE 3RD GLYCOGENOLYTIC PATHWAY

A unique anhydrohexulose, 1,5-anhydrofructose (1,5AnFru) has been dete cted in rat livers. Here we describe a microanalytical method for 1,5A nFru using GC/MS and report results on the distribution and production of 1,5AnFru in rats. The highest levels of 1,5AnFru were found in the liver (0.43 mu g/g wet tissue) and appreciable amounts were detected in adrenal gland and spleen (0.12 mu g/g and 0.09 mu g/g, respectively ). Other organs contained lower amounts while plasma contained virtual ly no detectable 1,5AnFru. We also demonstrated that 1,5AnFru is produ ced in the cytosol fraction of rat liver homogenate when an alpha-1,4- glucan or glycogen was added; 1,5AnFru was readily reduced to 1,5-anhy droglucitol with NADPH or at a reduced efficiency with NADH in the pre sence of a Mono Q chromatographic fraction obtained from the same cyto sol preparation. Based on these results, we propose the existence of a third degradation pathway, in addition to the phosphorolytic and hydr olytic reaction sequences, from glycogen to 1,5-anhydroglucitol via 1, 5AnFru in mammals. However, the physiological significance of 1,5AnFru and this putative minor glycogenolytic pathway in mammals remains obs cure.