Promotion and inhibition of α-amylase production in barley endosperm by cyclic 3',5'-adenosine monophosphate and adenosine diphosphate

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The possibility that gibberellin-induced α-amylase synthesis in barley endosperm might be mediated by cyclic-3',5'-adenosine monophosphate (3',5'-AMP) was examined. Promotion of α-amylase synthesis by 3',5'-AMP (5mM) was observed in the absence of gibberellic acid (GA_3) and in combination with GA_3 at concentrations below 2 mμM. When combined with gibberellin at concentrations above 2 mμM, however, 3',5'-AMP reduced the amount of α-amylase obtained. The cyclic nucleotide showed slight activity at concentrations as low as 0.05mM. These promotions were shown to be due. to increased synthesis of a-amylase rather than to an increased secretion of the enzyme. Of a variety of adenine compounds and nucleoside diphosphates tested only 3',5'-AMP and adenosine diphosphate (ADP) induced a-amylase synthesis. Longer incubation times were necessary to obtain maximal α-amylase induction with the nucleotides than with GA_3' ADP and 3',5'-AMP were about one third and one fifth as active, respectively, as GA_3 in promoting a-amylase synthesis, although GA_3 Was more than 107 times more effective. AMO-1618 did not inhibit the action of the nucleotides and methanolic extracts of the nucleotides showed no gibberellin-like activity. Both nucleotides were synergistic with GA_3 in overcoming the inhibitory effects of acetate and citrate buffers on a-amylase synthesis.
日本植物生理学会の論文