An NADP-dependent L-glutamate dehydrogenase from chloroplasts of Viciafaba L

Leech, Rachel M.; Kirk, Paul R.

doi:10.1016/0006-291x(68)90293-3

Cited by 64 publications

(28 citation statements)

References 11 publications

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“…The high specific activity and retention of 20% of the NADPH-glutamate dehydrogenase by the P2 fraction suggest that this enzyme is more tightly bound to the broken chlorolplasts than nitrite reductase. From this and other data (25), it was concluded that NADPH-glutamate dehydrogenase is located in the chloroplasts.…”

Section: Resultssupporting

confidence: 51%

“…As observed previously with the NADPH-glutamate dehydrogenase, little NADH activity was found in the P1 fraction. The presence of 80% of the total NADH activity in the supernatant may be attributed to the rupture of the mitochondria during isolation (25).…”

Section: Resultsmentioning

confidence: 99%

“…Further, the NADPH-dependent glutamate dehydrogenase, considered to be involved with the anabolic production of glutamate, is located in the chloroplasts (23,25,32).…”

mentioning

confidence: 99%

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Nitrite Assimilation and Amino Nitrogen Synthesis in Isolated Spinach Chloroplasts

Magalhães¹,

Neyra²,

Hageman³

1974

Plant Physiol.

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The assimilation of nitrite leading to de novo synthesis of amino nitrogen in a chloroplast-enriched fraction isolated from freshly harvested young spinach (Spinacia oleracea L.) leaves was demonstrated. The preparations showed approximately 55% intact chloroplasts as determined by light scattering properties and fixed C02 at rates of approximately 100 Amoles hr-mg chlorophyll1.The chloroplast-enriched fraction contained the enzymes, nitrite reductase and NADPH-glutamate dehydrogenase, needed for the reduction of nitrite and incorporation of ammonia into glutamate. Kinetic studies showed that the reduction of nitrite by the chloroplast-enriched fraction is light-dependent, and the process proceeds at rates of 6 to 12 Amoles hr-1 mg chlorophyll1. The addition of nitrite to the chloroplast preparation caused a 3-fold increase in the production of a-amino nitrogen when compared with the control without nitrite. There was a stoichiometric relation between amino-nitrogen synthesis and nitrite disappearance from the medium. The ratio of aminonitrogen :NO,-ranged from 0.6 to 0.9. The initial rate of amino-nitrogen production was faster when a-ketoglutarate was added to the nitrite reducing chloroplast medium than when it was omitted. However, these high rates were not sustained and the total amino-nitrogen production at the end of a 30-minute period was only slightly higher. These data show that chloroplasts are functionally able and contain the enzyme complement necessary to utilize light energy for the reduction of nitrite to amino nitrogen. Thus, chloroplasts should be considered as a major site for in vivo amino-nitrogen synthesis in green plants.

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Section: Resultssupporting

confidence: 51%

Section: Resultsmentioning

confidence: 99%

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Nitrite Assimilation and Amino Nitrogen Synthesis in Isolated Spinach Chloroplasts

Magalhães¹,

Neyra²,

Hageman³

1974

Plant Physiol.

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“…The results demonstrating the presence of amino transferases in chloroplasts raise a further question: why is "CO, incorporated into so few amino acids during photosynthesis in isolated chloroplasts despite the presence of the whole range of amino- Leaves of Vicia faba The crude chloroplast fraction was prepared as described in reference 35 and pure intact chloroplasts and lamellae as described previously (23 In order to test the possibility that the supply of carbon skeletons from the cytoplasm is a limiting factor in the amino acid biosynthesis in the chloroplast, we examined the supply of oxaloacetate to the chloroplast. The intracellular location of the enzymes catalyzing the conversion of 3-PGA to PEP was first examined.…”

Section: Methodsmentioning

confidence: 99%

“…An L-glutamate dehydrogenase would be able to catalyze the reductive amination of 2-ketoglutarate. Isolated chloroplasts have been shown to possess such an enzyme dependent on reduced pyridine nucleotides (23,30) and are capable of catalyzing the photoreduction of 2-ketoglutarate to glutamate (30,11). The recorded rates of photoreduction of 2-ketoglutarate by isolated chloroplasts are 0.…”

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confidence: 99%

Amino Acid Biosynthesis by Isolated Chloroplasts during Photosynthesis

Kirk

Leech

1972

Plant Physiol.

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The pool sizes of the common amino acids in purified intact chloroplasts from Vicia faba L. were measured (nanomoles per milligram chlorophyll). The three amino acids present in the highest concentrations were glutamate, aspartate, and threonine. Alanine, serine, and glycine were each present at levels between 15 and 20 nanomoles per milligram chlorophyll and 13 other amino acids were detectable at levels below 10.Only aspartate, alanine, glycine, serine, threonine, and lysine became labeled during photosynthetic "CO2 fixation by isolated chloroplasts: the label in aspartate represented over 60 % of the total '4C found in the amino acids. Glutamate dehydrogenase, glutamate-oxaloacetate, and glutamate-pyruvate aminotransferases were present in the chloroplasts, but no other trans. ferase activities from glutamate could be detected. The chloroplasts were able to synthesize a total of 17 other protein amino acids from either alanine or aspartate, but no synthesis of leucine by aminotransferase reactions could be detected. The synthesis of aspartate was studied in more detail. The enzyme systems required for the generation of oxaloacetate from triose phosphate were virtually absent from the chloroplasts but present in the leaf cytoplasmic fraction. Addition of either a leaf "cytoplasmic" fraction or an oxaloacetate generating system resulted in an increased proportion of the total "C fixed being found in the amino acid fraction during photosynthetic "CO2 fixation.It is suggested that the supply of oxaloacetate from the cytoplasm is one of the important factors controlling the synthesis of amino acids by the chloroplast.During "CO2 fixation in photosynthesizing algal cells (2,6,32) 2-ketoglutarate and that both the synthesis of glutamate and of alanine and aspartate probably take place within the chloroplast. An L-glutamate dehydrogenase would be able to catalyze the reductive amination of 2-ketoglutarate. Isolated chloroplasts have been shown to possess such an enzyme dependent on reduced pyridine nucleotides (23, 30) and are capable of catalyzing the photoreduction of 2-ketoglutarate to glutamate (30, 11). The recorded rates of photoreduction of 2-ketoglutarate by isolated chloroplasts are 0.4 ,umole/mg chl-hr (spinach [35]) and 0.6 ,umole/mg chl-hr (broad bean [11]). These low rates may partly account for the finding that, although chloroplasts can now be prepared which are capable of photosynthetic CO2 fixation at rates comparable with those observed in vivo (7,17,18), in general only 5 to 10% of the total radioactivity is recovered in the amino acid fraction (9,37). In isolated chloroplast suspensions aspartate (37), aspartate and alanine (9, 25), and glycine and serine (8) have been shown to be among the products of photosynthetic "CO2 fixation.Assuming the initial incorporation of ammonia in the chloroplast is into glutamate, a further question arises concerning the mode of transfer of the amino group from glutamate to the other amino acids. Amino transferase systems would provide a possible mechanism...

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Theanine: Its Occurrence and Metabolism in Tea

Li¹,

Silva

2018

Annual Plant Reviews Online

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Tea is the second most consumed beverage in the world, after water. It is widely regarded as a healthy beverage, associated with cancer prevention, boosting the immune system and mental alertness, although its popularity as a beverage probably has more to do with its pleasant taste and relaxation benefits. These qualities are attributed to a unique neurologically active non‐protein amino acid calledl‐theanine (γ‐ethylamino‐l‐glutamic acid). In this chapter, the authors review the properties of theanine, its occurrence and metabolism in tea. The possible role of theanine in nitrogen transport is discussed. The regulation of theanine levels is reviewed in the context of plant nitrogen metabolism. Particular emphasis is placed on the identification of enzymes involved in the synthesis and metabolism of theanine. Finally, the authors summarize the status of their endeavours to identify candidate genes contributing to the regulation of theanine levels in tea.

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An NADP-dependent L-glutamate dehydrogenase from chloroplasts of Viciafaba L

Cited by 64 publications

References 11 publications

Nitrite Assimilation and Amino Nitrogen Synthesis in Isolated Spinach Chloroplasts

Nitrite Assimilation and Amino Nitrogen Synthesis in Isolated Spinach Chloroplasts

Amino Acid Biosynthesis by Isolated Chloroplasts during Photosynthesis

Theanine: Its Occurrence and Metabolism in Tea

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