title: Hexose uptake regulation mediated through aerobic pathways: schism in a fibroblast mutant.
abstract: A protracted type of down-regulation of the hexose transport system in cultured fibroblasts that depends on one main factor in their nutritional state, the presence or absence of metabolizable D- aldohexoses in the culture fluid, is discussed. Fructose feeding is unable to elicit a down-regulation, whereas mannose and D-glucosamine, regulation of the transport system. This down-regulation or transport curb depends on oxidative energy metabolism, because inhibitors of this type of metabolism bring about a striking release of the transport curb. Studies with a fibroblast mutant that lacks the enzyme glucosephosphate isomerase (D-glucose-6-phosphate ketol-isomerase, EC 5.3.1.9, abbreviated phosphoglucose isomerase) (pgi-) have indicated that two types of metabolism are needed: 1) oxidative energy metabolism, which in the pgi- mutant can still be generated effectively from L-glutamine or, in its absence, from mannose or D-glucosamine; 2) glucose-6-phosphate metabolism, either its catabolism through the pentose shunt or through the anabolic pathway to UDP glucose and UDP galactose. The schism in carbohydrate metabolism in the pgi- fibroblasts is clearly reflected through the development of the metabolically mediated curb of the hexose transport or uptake system.
mesh_terms: D019325:3-O-Methylglucose; D000332:Aerobiosis; D000818:Animals; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D006224:Cricetinae; D003412:Cricetulus; D005347:Fibroblasts / Q000378:metabolism; D006601:Hexoses / Q000378:metabolism*; D007700:Kinetics; D008175:Lung Neoplasms; D008314:Malonates / Q000494:pharmacology; D008757:Methylglucosides / Q000378:metabolism; D009004:Monosaccharide Transport Proteins; D009154:Mutation
chemical_list: D002352:Carrier Proteins; D006601:Hexoses; D008314:Malonates; D008757:Methylglucosides; D009004:Monosaccharide Transport Proteins; D019325:3-O-Methylglucose; C030290:malonic acid