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

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.

Acetolactate Synthase Activity in Developing Maize (Zea mays L.) Kernels

“…3), similar to the patterns found for other enzymes of amino acid metabolism during endosperm development, including aspartate kinase (5), diaminopimelate decarboxylase (18), glutamine synthetase (4,8,11), glutamate synthase (11,19), threonine deaminase, and dihydrodipicolinic acid synthase (MJ Muhitch, unpublished data). These patterns suggest a coordinated regulation of gene expression for the enzymes of nitrogen assimilation and amino acid biosynthesis during maize endosperm development.…”

“…Studies with labeled amino acids also indicate that there is active nitrogen metabolism within the developing endosperm (17,20). Two recent reports (3,4) suggest that the embryo might also play a role in providing amino acids for endosperm storage synthesis in the later stages of kernel development.Leucine is one of the most abundant amino acids in mature maize endosperm (21 …”

Optimisation of Potassium Chloride Nutrition for Proper Growth, Physiological Development and Bioactive Component Production in Prunella vulgaris L

“…Glutamine synthetase (GS) activity was determined by means of the synthetase reaction [34]. The volume of the reaction mixture was 2.2 ml, including 0.5 ml of enzyme extract.…”

Effects of ammonium to nitrate ratio on growth, nitrogen metabolism, photosynthetic efficiency and bioactive phytochemical production ofPrunella vulgaris

“…Glutamine synthetase (GS; EC 6.3.1.2) activity was determined by the synthetase reaction (Hadži-Tašković Š ukalović, 1986). The volume of the reaction mixture was 2.2 mL, including 0.5 mL of enzyme extract.…”