Relationship between Ca2+ and L-asparagine in the induction of ornithine decarboxylase in H-35 rat hepatoma cells.
The activity of ornithine decarboxylase (ODC) in H-35 hepatoma cells depleted of Ca2+ by washing with 2 mM EGTA increased 35-fold after incubating for 4 h in a simple salt-glucose solution containing 10 mM L-asparagine and only if Ca2+ was replenished. Actinomycin D (5 micrograms/ml) and cycloheximide (20 microM) reduced the stimulatory effect by 84 and 100% respectively. Increase of active enzyme protein was also demonstrated by a 3-fold increase in alpha-difluoromethylornithine binding. Asparagine prolonged the half-life of induced ODC by 20% whereas Ca2+ reduced it by 32%. The observed inductive effects are not accounted for entirely by a direct influence of Ca2+ and asparagine on the turnover of ODC protein. These factors are likely to be parts of a signalling pathway leading to amplification of cellular ODC.
Hau
K P
KP
Department of Biochemistry, University of Hong Kong.
Wong
P C
PC
Fong
W F
WF
D000818:Animals; D001216:Asparagine / Q000494:pharmacology*; D002118:Calcium / Q000494:pharmacology*; D002412:Cations / Q000494:pharmacology; D003513:Cycloheximide / Q000494:pharmacology; D003609:Dactinomycin / Q000494:pharmacology; D000518:Eflornithine; D004790:Enzyme Induction / Q000187:drug effects; D006207:Half-Life; D008114:Liver Neoplasms, Experimental / Q000201:enzymology; D009955:Ornithine Decarboxylase / Q000096:biosynthesis*; D065108:Ornithine Decarboxylase Inhibitors; D051381:Rats; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000201:enzymology
D002412:Cations; D065108:Ornithine Decarboxylase Inhibitors; D003609:Dactinomycin; D001216:Asparagine; D003513:Cycloheximide; D009955:Ornithine Decarboxylase; D002118:Calcium; D000518:Eflornithine