Differential regulation by trophic conditions of phosphorylating and non-phosphorylating NADP(+)-dependent glyceraldehyde-3-phosphate dehydrogenases in Chlorella fusca.
The two NADP(+)-dependent glyceraldehyde-3-phosphate dehydrogenases present in the green alga Chlorella fusca, namely, the phosphorylating (chloroplastic) enzyme and the non-phosphorylating (cytosolic) enzyme, are differently affected by the trophic conditions prevailing in the cell cultures. The addition of metabolizable sugars to cell cultures growing in the light promotes a marked decrease of the phosphorylating enzyme activity down to a barely detectable cellular level. In contrast, the cellular level of the non-phosphorylating enzyme is even enhanced in the presence of such sugars. These effects are not observed, however, with a number of non-assimilable sugar analogs. After sugar removal, a recovery of the phosphorylating activity--in a process which is inhibited by cycloheximide but not by lincomycin--is observed in illuminated cells but not in darkness, thus indicating a light-dependent nuclear synthesis of the chloroplastic enzyme. It seems therefore that the two dehydrogenases are adaptative enzymes subject to differential regulation by nutritional conditions.
Serrano
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Instituto de Bioquímica Vegetal y Fotosíntesis, Universidad de Sevilla, Spain.
Mateos
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Losada
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D002241:Carbohydrates / Q000494:pharmacology; D002474:Cell-Free System; D002708:Chlorella / Q000201:enzymology* / Q000528:radiation effects; D003624:Darkness; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases / Q000378:metabolism*; D007527:Isoenzymes / Q000378:metabolism*; D007700:Kinetics; D008027:Light; D009249:NADP / Q000378:metabolism; D010766:Phosphorylation
D002241:Carbohydrates; D007527:Isoenzymes; D009249:NADP; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases