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. 1980 Oct;66(4):782–786. doi: 10.1104/pp.66.4.782

Changes in Activities of Enzymes of Nitrogen Metabolism in Seedcoats and Cotyledons during Embryo Development in Pea Seeds 1

David R Murray 1,2, Ivan R Kennedy 1,2
PMCID: PMC440722  PMID: 16661521

Abstract

In the seedcoats of developing pea seeds, the maximal activities of asparaginase (EC 3.5.1.1) and aspartate: α-ketoglutarate aminotransferase (EC 2.6.1.1) are attained early in development, before the embryo has expanded to fill the embryo sac. These two enzyme activities could account for the early absence of asparagine and aspartate from the fluid secreted by the seedcoats into the embryo sac.

Changes in the activities of alanine: α-ketoglutarate aminotransferase (EC 2.6.1.2), glutamate dehydrogenase (EC 1.4.1.3), glutamine synthetase (EC 6.3.1.2), and glutamate synthase (EC 1.4.1.13) have also been measured, in cotyledons as well as seedcoats. On a fresh weight basis, the highest activities of asparaginase and both aminotransferases developed in the seedcoats, whereas the highest activities of the remaining enzymes developed in the cotyledons.

The data indicate that the amide groups of imported asparagine and glutamine are metabolized differently, largely by asparaginase and glutamate synthase, respectively. The NH4+ released by the action of asparaginase is evidently reassimilated in cotyledon cells by the joint action of glutamate dehydrogenase, glutamine synthetase, and glutamate synthase. The data emphasize the central importance of α-ketoglutarate-glutamate cycling in the redistribution of amino groups associated with the net synthesis of amino acids and reserve proteins.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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