TY - JOUR
T1 - Genetic regulation of galactokinase in Tetrahymena by cyclic AMP, glucose, and epinephrine
AU - Roberts, C. T.
AU - Morse, D. E.
PY - 1978
Y1 - 1978
N2 - The authors have found evidence that transcription of the galactokinase (ATP:D-galactose 1-phosphotransferase; EC 2.7.1.6) gene is inhibited, in the animal-like protozoan Tetrahymena, by dibutyryl adenosine 3':5'-cyclic monophosphate, glucose, and epinephrine.The specific activities of galactokinase in Tetrahymena cells grown in defined media with galactose or glycerol as the principal carbon source are equivalent; the specific activity in glucose minimal medium is 1/7 the value. Thus, while there seems to be no specific induction of the enzyme by the substrate, galactose, there is a strong 'repression' by glucose. This repression by glucose is mimicked, in glycerol-grown cells, by the addition of millimolar amounts of dibutyryl adenosine 3':5'-cyclic monophosphate or phosphodiesterase inhibitors such as caffeine and theophylline. When glucose-grown cells are washed and resuspended in carbohydrate-free medium, the galactokinase specific activity increases by as much as 10-fold within 12 hr. This increase is blocked by dibutyryl adenosine 3':5'-cyclic monophosphate and by epinephrine (synthesized by Tetrahymena, and previously shown to activate a membrane-bound adenylate cyclase in extracts of this organism), as well as by inhibitors of mRNA synthesis, maturation, and translation. The results suggest that glucose and epinephrine can regulate transcription of the galactokinase gene by modulation of cyclic nycleotide levels. The observation that the nonmetabolized sugars 2-deoxyglucose, 2-deoxygalactose, and α-methylglucoside are as effective as glucose suggests that the sugar itself, or an immediate metabolite such as the 1-phosphate derivative, may be the effector.
AB - The authors have found evidence that transcription of the galactokinase (ATP:D-galactose 1-phosphotransferase; EC 2.7.1.6) gene is inhibited, in the animal-like protozoan Tetrahymena, by dibutyryl adenosine 3':5'-cyclic monophosphate, glucose, and epinephrine.The specific activities of galactokinase in Tetrahymena cells grown in defined media with galactose or glycerol as the principal carbon source are equivalent; the specific activity in glucose minimal medium is 1/7 the value. Thus, while there seems to be no specific induction of the enzyme by the substrate, galactose, there is a strong 'repression' by glucose. This repression by glucose is mimicked, in glycerol-grown cells, by the addition of millimolar amounts of dibutyryl adenosine 3':5'-cyclic monophosphate or phosphodiesterase inhibitors such as caffeine and theophylline. When glucose-grown cells are washed and resuspended in carbohydrate-free medium, the galactokinase specific activity increases by as much as 10-fold within 12 hr. This increase is blocked by dibutyryl adenosine 3':5'-cyclic monophosphate and by epinephrine (synthesized by Tetrahymena, and previously shown to activate a membrane-bound adenylate cyclase in extracts of this organism), as well as by inhibitors of mRNA synthesis, maturation, and translation. The results suggest that glucose and epinephrine can regulate transcription of the galactokinase gene by modulation of cyclic nycleotide levels. The observation that the nonmetabolized sugars 2-deoxyglucose, 2-deoxygalactose, and α-methylglucoside are as effective as glucose suggests that the sugar itself, or an immediate metabolite such as the 1-phosphate derivative, may be the effector.
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U2 - 10.1073/pnas.75.4.1810
DO - 10.1073/pnas.75.4.1810
M3 - Article
C2 - 205871
AN - SCOPUS:0018149879
SN - 0027-8424
VL - 75
SP - 1810
EP - 1814
JO - Proceedings of the National Academy of Sciences of the United States of America
JF - Proceedings of the National Academy of Sciences of the United States of America
IS - 4
ER -