Anomeric specificity of D-glucose metabolism in rat brain cells

Rat brain cells were incubated at 9 degrees C (and occasionally at 37 degrees C) in the presence of the anomers of D-[5-3H]glucose, D-[U-14C]glucose, D-[6-14C]glucose and D-[1-14C]glucose (1.0 mM). The utilization of beta-D-[5-3H]glucose was slightly higher than that of alpha-D-[5-3H]glucose, a situation possibly attributable to the anomeric behaviour of hexokinase. However, the production of 14CO2 from the alpha-anomer always largely exceeded that from the beta-anomer. The anomeric difference in D-[U-14C]glucose oxidation, relative to D-[5-3H]glucose utilization, was suppressed in the presence of NH4Cl. Even at anomeric equilibrium, the relative contribution of alpha-D-glucose to 14CO2 output exceeded its relative abundance. The beta/alpha ratio for D-[1-14C]glucose oxidation (or D-[U-14C]glucose oxidation) was higher than that for D-[6-14C]glucose oxidation. Comparable observations were made in brain cells from albino rats and either lean or obese Zucker rats. It is concluded that D-glucose metabolism displays anomeric specificity in rat brain cells, even when the latter are exposed to equilibrated D-glucose. It is also speculated that anomeric differences in the phosphorylation of D-glucose by bound hexokinase may directly influence mitochondrial oxidative events.