Glutamate dehydrogenases of unicellular green algae: Effects on nitrate and ammonium in vivo

Shatilov, V. R.; Sof’in, A. V.; Kasatkina, T.I.; Zabrodina, T.M.; Vladimirova, M. G.; Semenenko, V. E.; Kretovich, W. L.

doi:10.1016/0304-4211(78)90113-x

Cited by 11 publications

(6 citation statements)

References 8 publications

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“…As with several other species of Chlorella (20,22,23,27), GDH in C. autotrophica appears to be present in two forms, a constitutive GDH which has low nucleotide specificity (22,27), and an inducible form highly specific for NADPH. Cells grown on NO3-appear to contain only the constitutive form, whereas the inducible NADPH-GDH is present in NH4+-grown cells, and increasing levels ofthis form were observed with increasing NH4' concentration (Table II).…”

Section: Discussionmentioning

confidence: 99%

“…Also, for some microalgae such as Platymonas striata (7) and Chiamydomonas reinhardii (6), only the activities of GS and GOGAT were found to be sufficient to carry out the required rate of nitrogen assimilation. However, many microalgae contain high levels ofGDH activities (9,20,(22)(23)(24)27) provided by Everest and Syrett (9) for NO3-grown Stichococcus bacillaris which has an inducible NADPH-GDH with a low Km for NH4' (KmaPP, 1 mM). Several strains of Chlorella are also found to contain an inducible NADPH-GDH; however, in this case the enzyme is synthesized in NH4-grown cells (9,20,22,23,27).…”

Section: Introductionmentioning

confidence: 99%

“…Several strains of Chlorella are also found to contain an inducible NADPH-GDH; however, in this case the enzyme is synthesized in NH4-grown cells (9,20,22,23,27). Shatilov and Kretovich (22) have proposed that this GDH might have a role in NH41 assimilation of Chlorella under conditions ofhigh NH41 availability.…”

mentioning

confidence: 99%

“…Also, for some microalgae such as Platymonas striata (7) and Chiamydomonas reinhardii (6), only the activities of GS and GOGAT were found to be sufficient to carry out the required rate of nitrogen assimilation. However, many microalgae contain high levels ofGDH activities (9,20,(22)(23)(24)27) indicating a potential role for this enzyme in NH4' assimilation. The only clear evidence to date of the participation of GDH in NH4' assimilation by green algae has been ' Supported by Grant A6032 from Natural Sciences and Engineering…”

mentioning

confidence: 99%

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Nitrogen Metabolism of the Marine Microalga Chlorella autotrophica

Ahmad

Hellebust²

1984

Plant Physiol.

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The levels of glutamine synthetase (GS) and glutamate dehydrogenase (GDH) in Chlorella autotrophica (clone 580) are strongly regulated by the nitrogen source and salt concentration of the medium. GS is present at high levels in NOj--grown cells, and at maximum levels in nitrogenstarved cells. However, the levels of GS in these cells are somewhat decreased by increasing salinity. Cells growing on NH4W have high NADPH-GDH activity, the levels of which increase with increasing NH4' supply, while GS decreases to a very low level under these conditions. Salinity intensifies the induction of NADPH-GDH activity in NH4V-grown cells. The levels of NADH-GDH are low in this alga, but present under all growth conditions. Methionine sulfoximine (MSX) has little effect on growth and nitrogen assimilation ofthe alga in the presence of NW.Numerous studies have dealt with the uptake and utilization by marine microalgae of various nitrogen sources found in seawater (5,8,14,17,26). However, only a few of these have focused on metabolic pathways of nitrogen assimilation in these organisms (3,7,26). Furthermore, there appears to be a need to examine nitrogen assimilation in microalgae in relation to metabolic adaptation to salinity fluctuations. This consideration is particularly important for euryhaline microalgae which are subject to rapid changes in salinity in their natural environments (2). Metabolic activities such as photosynthesis have been shown to react to changes in external salt concentrations (4, 10, 13), but little is known about the effect of external salinity on nitrogen assimilation in microalgae.Eukaryotic green plants have the enzymic potential for the assimilation of NH4' by the reductive amination of 2-oxoglutarate either by GDH2 or by the combined action of GS and GOGAT (19,24,26). In higher plants, the GS-GOGAT cycle appears to be the primary pathway of NH4' assimilation, and GDH plays only a minor role (19,24). Also, for some microalgae such as Platymonas striata (7) and Chiamydomonas reinhardii (6), only the activities of GS and GOGAT were found to be sufficient to carry out the required rate of nitrogen assimilation. However, many microalgae contain high levels ofGDH activities (9,20,(22)(23)(24)27) provided by Everest and Syrett (9) for NO3-grown Stichococcus bacillaris which has an inducible NADPH-GDH with a low Km for NH4' (KmaPP, 1 mM). Several strains of Chlorella are also found to contain an inducible NADPH-GDH; however, in this case the enzyme is synthesized in NH4-grown cells (9,20,22,23,27). Shatilov and Kretovich (22) (9) have also shown that C. vulgaris cannot utilize NH4' in the presence of MSX. However, the lack of NH4' assimilation by MSX-treated cells of C. vulgaris shown in their study does not necessarily exclude a role for NADPH-GDH in NH41 assimilation of this alga, as the experimental conditions used were such that the activity of NADPH-GDH disappeared rapidly in both cells incubated with or without MSX.In this report, we present a study of nitrogen assimilation by the euryhali...

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

“…Also, for some microalgae such as Platymonas striata (7) and Chiamydomonas reinhardii (6), only the activities of GS and GOGAT were found to be sufficient to carry out the required rate of nitrogen assimilation. However, many microalgae contain high levels ofGDH activities (9,20,(22)(23)(24)27) indicating a potential role for this enzyme in NH4' assimilation. The only clear evidence to date of the participation of GDH in NH4' assimilation by green algae has been ' Supported by Grant A6032 from Natural Sciences and Engineering…”

mentioning

confidence: 99%

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Nitrogen Metabolism of the Marine Microalga Chlorella autotrophica

Ahmad

Hellebust²

1984

Plant Physiol.

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“…The magnitude of the change in activity of biosynthetic glutamine synthetase is much less than the change in asparaginase, however, Previous work (20) (14) and Talley (31) who found that high concentrations of ammonium induced an NADPH-dependent glutamate dehydrogenase electrophoretically distinct from an NADH-dependent enzyme in Chlorella pyrenoidosa. Shatilov et al (29) found a constitutive glutamate dehydrogenase active with both NADH and NADPH in a variety of unicellular green algae. Several of these organisms possessed an ammonium-inducible NADPH-specific glutamate dehydrogenase (29) while others did not.…”

Section: Discussionmentioning

confidence: 99%

Regulation of Asparaginase, Glutamine Synthetase, and Glutamate Dehydrogenase in Response to Medium Nitrogen Concentrations in a Euryhaline Chlamydomonas Species

Paul¹,

Cooksey²

1981

Plant Physiol.

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The ammonium assimilatory enzymes glutamine synthetase (EC 6.3.1.2) and glutamate dehydrogenase (EC IA.41.3) were investigated for a possible role in the regulation of asparaginase (EC 3.5.1.1) in a Chiamydomonas species isolated from a marine environment. Cells grown under nitrogen limitation (0.1 milimolar NH4', NOs-, or L-asparagine) possessed 6 times the asparaginase activity and approximately one-half the protein of cells grown at high nitrogen levels (1.5 to 2.5 mlHlmolar). Biosynthetic glutamine synthetase activity was 1.5 to 1.8 times greater in nitrogen-limited cells than cells grown at high levels of the three nitrogen sources.Conversely, glutamate dehydrogenase (both NADH-and NADPH-dependent activities) was greatest in cells grown at high levels of asparagine or ammonium, while nitrate-grown cells possessed little activity at all concentrations employed. For all three nitrogen sources, glutamate dehydrogenase activity was correlated to the residual ammonium concentration of the media after growth (r = 0.88 and 0.94 for NADH-and NADPHdependent activities, respectively).These results suggest that glutamate dehydrogenase is regulated in response to ambient ammonium levels via a mechanism distinct from asparaginase or glutamine synthetase. Glutamine synthetase and asparaginase, apparentiy repressed by high levels of all three nitrogen sources, are perhaps regulated by a common mechanism responding to intracellular nitrogen depletion, as evidenced by low cellular protein content.ling its synthesis in eukaryotic microalgae are not known. Nitrogen deprivation has been shown to cause an increase in L-asparaginase levels in Saccharomyces cerevisae (9, 22), Aspergillus nidulans (8), and Klebsiella aerogenes (25). Conditions which led to derepression of glutamine synthetase (i.e. nitrogen deprivation) also led to derepression of L-asparaginase in K. aerogenes and mutants constitutive for glutamine synthetase were also constitutive for asparaginase (25).Recently, we described the first algal L-asparaginase in a euryhaline Chlamydomonas species (21). This organism could only utilize asparagine, glutamine, ammonium, or nitrate as sole nitro- MATERIALS AND METHODSThe enzyme L-asparaginase (EC 3.5.1.1) has been investigated extensively in bacteria, fungi, and certain mammals because of its importance as an antineoplastic agent (for reviews see 7, 33). LAsparagine has been described as a major nitrogen transport and storage compound in legumes (3) and L-asparaginase may play a major role in the mobilization of the amide nitrogen for utilization in amino acid and protein synthesis in higher plants (see 19 for review). Recently, a potassium-dependent L-asparaginase has been described in tissues of several higher plants (30) indicating that the distribution of asparaginase among higher plants may be more widespread than previously thought.Although L-asparaginase regulation has been studied extensively in bacteria (4,11,12,15)

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Occurrence of glutamate dehydrogenase isoenzymes during growth of Oocystis alga

Lee

Picard

1983

Biotech & Bioengineering

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Oocystis sp., a unicellular green alga, contained two glutamate dehydrogenase isoenzymes: one was specific for NADH and the other for NADPH. Activity staining after gel electrophoresis indicated that one component in NADH-GDH was not specific for the cofactor and three components in NADPH-GDH. The optimal concentration of substrate, purification procedure and kinetic properties of both glutamate dehydrogenase (GDH) enzymes in vitro are presented. The kinetics of growth, nutrient removal and enzyme activities for Oocystis growing in wastewater showed that ammonia was preferentially utilized over nitrate and the medium was depleted before the maximum population was obtained in indoor culture. There was a sharp increase in NADPH-GDH activity following the exhaustion of ammonia from the medium but NADH-GDH activity remained unchanged. The NADPH-GDH activity at the outset increased exponentially with time in greenhouse culture but then decreased sharply accompanied by a rapid increase in biomass and nitrite concentration. The K(m) values for ammonia in this algal GDH was high, while glutamate synthase activity was not detected; this suggests that Oocystis may adapt to conditions of ammonia limitation by producing large quantities of NADPH-GDH instead of using glutamate synthase pathway.

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Glutamate dehydrogenases of unicellular green algae: Effects on nitrate and ammonium in vivo

Cited by 11 publications

References 8 publications

Nitrogen Metabolism of the Marine Microalga Chlorella autotrophica

Nitrogen Metabolism of the Marine Microalga Chlorella autotrophica

Regulation of Asparaginase, Glutamine Synthetase, and Glutamate Dehydrogenase in Response to Medium Nitrogen Concentrations in a Euryhaline Chlamydomonas Species

Occurrence of glutamate dehydrogenase isoenzymes during growth of Oocystis alga

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