Abstract
When treated with protopine and alkalized extracts of the tuber of Corydalis ternata for one year, significant decrease in glutamate level and increase in glutamate dehydrogenase (GDH) activity was observed in rat brains. The expression of GDH between the two groups remained unchanged as determined by Western and Northern blot analysis, suggesting a post-translational regulation of GDH activity in alkalized extracts treated rat brains. The stimulatory effects of alkalized extracts and protopine on the GDH activity was further examined in vitro with two types of human GDH isozymes, hGDH1 (house-keeping GDH) and hGDH2 (nerve-specific GDH). Alkalized extracts and protopine activated the human GDH isozymes up to 4.8-fold. hGDH2 (nerve- specific GDH) was more sensitively affected by 1 mM ADP than hGDH1 (house-keeping GDH) on the activation by alkalized extracts. Studies with cassette mutagenesis at ADP-binding site showed that hGDH2 was more sensitively regulated by ADP than hGDH1 on the activation by Corydalis ternata. Our results suggest that prolonged exposure to Corydalis ternata may be one of the ways to regulate glutamate concentration in brain through the activation of GDH.
Highlights
Glutamate dehydrogenase (GDH) (EC 1.4.1.3) is a family of enzymes catalyzing a reversible deamination of L-glutamate to α-ketoglutarate
We present the effects of protopine and alkalized extracts of the C. ternata on GDH in vivo and in vitro in view of the central role of GDH in cerebral metabolism
To examine the long-term effects of C. ternata on glutamate level and activities of the enzymes involved in glutamate metabolism in rat brain, rats were kept in equal groups with or without protopine and alkalized extracts for one yr
Summary
Glutamate dehydrogenase (GDH) (EC 1.4.1.3) is a family of enzymes catalyzing a reversible deamination of L-glutamate to α-ketoglutarate. Stimulation studies with alkalized extracts or protopine were performed at various concentrations in assay buffer at 25oC as described in figure legends. To examine the long-term effects of C. ternata on glutamate level and activities of the enzymes involved in glutamate metabolism in rat brain, rats were kept in equal groups with or without protopine and alkalized extracts for one yr.
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