Structure and Function of Glutamate Dehydrogenase During Transient Senescence of Mustard (Sinapis Alba L.) Cotyledons
Glutamate dehydrogenase (GDH, EC 188.8.131.52) catalyses the reductive amination of 2-oxoglutarate to glutamate (NADH-GDH) especially under conditions of ample ammonia supply (Yamaya and Oaks, 1987). This enzyme seems to be ubiquitous in almost all species of higher plants and is recognized to have a regulatory position as a link between carbohydrate and amino acid metabolism. It is known to exhibit a complex isoform pattern (Nauen and Hartmann, 1980) which differs in various parts of the plant (Cammaerts and Jacobs, 1985) and depends on the developmental stage (Laurière, 1983) and on light treatment (Postius and Jacobi, 1976). An increase in GDH activity during leaf senescence (SEN) appears to be a general feature (Srivastava and Singh, 1987; Laurière, 1983) and it has been suggested that ammonia produced by proteolysis during SEN could be a regulatory factor for de novo synthesis of the enzyme. Kar and Feierabend (1984) demonstrated with detached wheat leaves that an increase in GDH activity followed a control mechanism which governed also the time course of SEN.
KeywordsLeaf Senescence Glutamate Dehydrogenase Aminating Activity Mustard Seedling Subunit mRNA Level
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