Regulatory effects of ammonia on carbon metabolism in photosynthesizing Chlorella pyrenoidosa

Kanazawa, Tamotsu; Kirk, Martha; Bassham, James A.

doi:10.1016/0005-2728(70)90106-4

Cited by 106 publications

(69 citation statements)

References 11 publications

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“…Recently, with Chlorella, Kanazawa et al (6,7) have studied the effect of NH4+ on the metabolic pool sizes of photosynthetic products. They observed an increase in amino acids and a decrease in sucrose, not only due to the increased availability of NH,' for reductive amination but also due to an apparent activation of the pyruvate kinase by NH4+.…”

Section: Resultsmentioning

confidence: 99%

Metabolism of Separated Leaf Cells

Rehfeld

Jensen²

1973

Plant Physiol.

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Separated mesophyll cells from cotton (Gossypium hirsutum var. Stoneville 1613 Glandless) were isolated with pectinase and mechanical agitation. The separated cells had rates of light-dependent C02 fixation between 50 to 100 umoles COa per mg chlorophyll per hour. The presence of Ca'+ in the incubation medium did not significantly affect the type of photosynthetic products formed, but 2 mM Cae+ did cause a 50% decrease in the appearance of photosynthetic products in the incubation medium. The movement of all types of products (sugars, organic, and amino acids) out of the cells was reduced similarly by the Ca'+. Light had no affect on the movement of products out of the cells, whereas 1 mM ethylenediaminetetraacetate greatly increased the movement. The addition of 1.6 mM NH4Cl to the cell suspensions caused a large increase in the amount of fixed 14C appearing in the amino acid fraction and a decrease in the sugar fraction. These metabolic changes in the cells were reflected in the movement of products out of the cells so that the incubation medium also contained a larger amount of label in amino acids and a smaller amount in sucrose. Although the cell plasma membrane restricted the movement of soluble products, it did not discrminate significantly between the types of products moved.Techniques have recently been developed in this laboratory (3, 5) and others (13) for the isolation of separated mesophyll cells by use of a crude pectinase preparation. These separated cells are capable of photosynthetic CO2 fixation for 20 or more hours with formation of products similar to those found in leaf tissue (5). The cells are capable of taking up amino acids and uracil and uridine from the incubation medium and incorporating them into proteins and RNA, respectively (3). The use of separated cells for the study of leaf metabolism offers at least two advantages. First, the cells can be handled similarly to unicellular algae, thus facilitating the removal of uniform aliquots. Second, and more importantly, all cells in

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Section: Resultsmentioning

confidence: 99%

Metabolism of Separated Leaf Cells

Rehfeld

Jensen²

1973

Plant Physiol.

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“…The results of the experiments described in this paper would (19) that ammonia can regulate the activity of pyruvate kinase in whole Chlorella cells is therefore of particular interest. Several workers have reported that the application of ammonia to photosynthesizing whole cells stimulates the incorporation of "4CO2 into amino acids (15,19,26).…”

Section: Methodsmentioning

confidence: 94%

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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“…Biochemical evidence suggests that at least some TCA-cycle carbon flow is maintained in the light (e.g. Marsh et al 1965;Kanazawa et al 1970;Birch et al 1986;Elrifi and Tut-pin 1987;McCashin et al 1988), but it has been proposed that an increase in the ATP : ADP ratio during photosynthesis would result in inhibition of mitochondrial electron transport and that other processes would be responsible for NADH oxidation (Graham 1980). Stitt et al (1982) have shown, however, that light-dark transitions have little effect on cellular ATP : ADP.…”

Section: Acknowledgmentsmentioning

confidence: 99%

Respiratory losses in the light in a marine diatom: Measurements by short‐term mass spectrometry

Weger

Herzig

Falkowski

et al. 1989

Limnology & Oceanography

125

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Mass spectrometric analysis of gas exchange by the diatom Thalassiosira weisflogii grown under at the end of scotophase. When cells were poised at the DIC (dissolved inorganic carbon) compensation point in the light (DIC concentration where net photosynthesis equals zero), mitochondrial 0, consumption was only slightly higher than in the dark. Adding DIC to cells at the compensation point resulted in a rapid increase in both photosynthetic 0, evolution and mitochondrial 0, consumption, indicating that the higher mitochondrial respiration rates observed in the light are probably due to an increase in substrate supply from photosynthesis. If estimates of primary production are based on oxygen exchange, this effect is accounted for; however if radiocarbon is used to measure production, especially in short-term measurements, net production may be significantly overestimated.Phytoplankton respiration is used in aquatic ecology to quantify at least three fundamental parameters. First, knowledge of the rate of respiratory losses is required ' To whom reprint requests should be addressed.

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Regulatory effects of ammonia on carbon metabolism in photosynthesizing Chlorella pyrenoidosa

Cited by 106 publications

References 11 publications

Metabolism of Separated Leaf Cells

Metabolism of Separated Leaf Cells

Amino Acid Biosynthesis by Isolated Chloroplasts during Photosynthesis

Respiratory losses in the light in a marine diatom: Measurements by short‐term mass spectrometry

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