The changes in enzyme activities in embryonic axes of soybean seeds during germination were investigated. After 48 hr of germination, the activities of 6-phosphogluconate, glucose-6-phosphate, and L-isocitrate dehydrogenases were 2-4 times as high those of embryonic axes from dry seeds. The activities of L-glutamate and meso-D-diaminopimelate dehydrogenases and of L-isocitritase, however, were still low. The activities of L-malate dehydrogenase and acid phosphatase increased strikingly after germination, and the activities of the germinated axes were about 80 (at 48 hr) and 27 (at 40 hr) times, respectively, those of embryonic axes from dry seeds. The elevated activity of acid phosphatase was due to de novo synthesis of enzyme protein in the embryonic axes, not to activation of the enzyme protein, or to transfer of the enzyme protein from germinating cotyledons. Acid phosphatase activity in embryonic axes increased in a very early stage of protein synthesis in the axes. The pronounced increase in L-malate dehydrogenase activity was mainly due to activation of the enzyme protein by imbibition, not to de novo synthesis of enzyme protein, or to transfer of the enzyme protein from germinating cotyledons.
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