Activity and distribution of nitrogen‐metabolism enzymes in the developing maize kernel

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Abstract
The activities of glutamine synthetase (EC 6.3.1.2), glutamate dehydrogenase (EC 1.4.1.2), aspartate aminotransferase (EC 2.6.1.1), alanine aminotransferase (EC 2.6.1.2) and soluble protein content in the developing endosperm and embryo of normal (Oh‐43) and mutant (Oh‐4302) maize were investigated. Maize inbred lines were grown under field conditions and all plants were self‐pollinated. Ears for experiments were harvested over the period of 15 lo 45 days after pollination. After pollination kernel capacity for soluble protein synthesis is located mainly in the endosperm. This progressively decreases and about 40 days after pollination soluble protein synthesis is taken over by the embryo. Comparative data on the activity of the investigated enzymes in the embryo and endosperm indicate that the capacity for synthesis of glutamine and glutamate predominates in the embryo tissue, whereas transamination processes at the initial stages of the embryo development are less intensive than their counterparts in the endosperm. The roles of embryo and endosperm subsequently interchange. Biosynthetic processes of soluble precursors for protein synthesis in the embryo and endosperm of the developing kernel are mutually coordinated.