Age-dependent changes in glucose 1,6-bisphosphate levels and in the activities of glucose 1,6-bisphosphatase, and particulate hexokinase and 6-phosphogluconate dehydrogenase in rat skin.
The levels of glucose 1,6-bisphosphate (Glc-1,6-P2), the powerful regulator of carbohydrate metabolism, changed in rat skin during growth: Glc-1,6-P2 increased during the first week of age, and thereafter was dramatically reduced during maturation. The activity of glucose 1,6-bisphosphatase, the enzyme that degradates Glc-1,6-P2, changed with age in an invert manner as compared to the changes in Glc-1,6-P2. These findings suggest that the age dependent changes in this enzyme's activity may account for the changes in intracellular Glc-1,6-P2 concentration. The age-related changes in Glc-1,6-P2 were accompanied by concomitant changes in the activities of particulate (mitochondrial) hexokinase and 6-phosphogluconate dehydrogenase, the two enzymes known to be inhibited by Glc-1,6-P2. The activities of both these enzymes in the soluble fraction were not changed with age. The particulate enzymes were more susceptible to inhibition by Glc-1,6-P2 than the soluble activities, which may explain why only the particulate, but not the soluble activities, correlated with the age-dependent changes in tissue Glc-1,6-P2. These results suggest that the changes in particulate hexokinase and 6-phosphogluconate dehydrogenase resulted from changes in intracellular concentration of Glc-1,6-P2. The marked reduction in Glc-1,6-P2 during maturation, accompanied by activation of mitochondrial hexokinase and 6-phosphogluconate dehydrogenase, may reflect an enhancement in skin metabolism during growth.
D000375:Aging; D000818:Animals; D019298:Glucose-6-Phosphate / Q000031:analogs & derivatives*; D005958:Glucosephosphates / Q000378:metabolism*; D006593:Hexokinase / Q000378:metabolism; D010734:Phosphogluconate Dehydrogenase / Q000378:metabolism; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism; D051381:Rats; D012867:Skin / Q000201:enzymology / Q000378:metabolism*
D005958:Glucosephosphates; D019298:Glucose-6-Phosphate; C016473:glucose-1,6-bisphosphate; D010734:Phosphogluconate Dehydrogenase; D006593:Hexokinase; C014818:glucose 1,6-diphosphate phosphatase; D010744:Phosphoric Monoester Hydrolases