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 4h in a simple salt-glucose solution containing 10 mM L-asparagine and only if Ca2+ was replenished. Actinomycin D (5 μg/ml) and cycloheximide (20 μM) reduced the stimulatory effect by 84 and 100% respectively. Increase of active enzyme protein was also demonstrated by a 3-fold increase in α-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.
|Number of pages||11|
|Publication status||Published - 1992|
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