Blue light photoreactivation of nitrate reductase from green algae and higher plants

Aparicio, Pedro J.; Roldán, JoséM.; Calero, Fernando Sánchez

doi:10.1016/0006-291x(76)91011-1

Cited by 85 publications

(30 citation statements)

References 16 publications

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“…The observed initial lag on photoreactivation might be due to the presence in the cellfree extract of some internal reductants that, like ascorbate or reduced pyridine nucleotides, may quench excited flavins before they become completely photooxidized (24). As descibed elsewhere for the Chlorella nitrate reductase (2), these data show that blue light is capable of activating the inactive form of the Chla- nitrogen metabolism appears to be photochromically regulated, inasmuch as cells under these conditions consume NO3-and release to the culture medium a major portion of the N03-reduction products, namely N02-and HN4', at much higher rates under blue than under red light. In this regard, preliminary results indicate that Chlorella pyrenoidosa also behaves similarly.…”

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confidence: 76%

In Vivo Blue-Light Activation of Chlamydomonas reinhardii Nitrate Reductase

Azuara¹,

Aparicio²

1983

Plant Physiol.

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CMldmyuOnas rihardii cells, growning photoautotropbical under air, excreted to the culture medium much higher amounts of N02 and NH4 I under ble than under red fight. Under shmilar conditions, but with N02-as the only nitrogen source, the cells consumed NO2 -and excreted NH4, at shilar rates under blue and red light. In the presence of N03-and air with 2% CO2 (v/v) incorporate al the pbotogenerated NH4 +. Because these cells should have high levels of reducing power, they might use N03-or, in its absence, NO,-as terminal electron acceptors. The excretion of the products of N02-and NH4, to the medium may provide a mechanism to control reductant level in the cells. Blue lght is suggested as an important regulatory factor of this photorespiratory conmption of N03-and possibly of the whole nitrogen metabolism in green algae.Nitrate assimilation in green algae and higher plants is a basic metabolic process because it uses more than 20o of the reducing power generated by their photosynthetic apparatus (11). Among the different steps involved in this metabolic pathway, reduction of NO3 to N02 catalyzed by nitrate reductase has become particularly relevant due to its regulatory features on nitrogen metabolism (5,12,36).NADH-nitrate reductase from green algae is a multimeric enzyme of high mol wt with several electron transport components such as flavin adenine dinucleotide, protoheme b557, and molybdenum (8). Recently, it has been reported that molybdenum is held in a special cofactor that contains an unidentified pterin (13).

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confidence: 76%

In Vivo Blue-Light Activation of Chlamydomonas reinhardii Nitrate Reductase

Azuara¹,

Aparicio²

1983

Plant Physiol.

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“…In a study on the reactivation of spinach leaf NR, it was established that blue light was most effective (2). It has been proposed (1) that the FAD in the NR complex absorbs the blue light and after light excitation, it oxidizes the enzyme complex.…”

Section: Discussionmentioning

confidence: 99%

“…The inactivation is mediated by the binding of a low level of cyanide (.l0-10M) to the molybdenum of the reduced enzyme, blocking electron transfer to nitrate. Rapid reactivation of NR occurs when it is oxidized by ferricyanide (17) or exposed to blue light in the presence of FAD (2). A slow reactivation is obtained by incubation with nitrate (17).…”

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confidence: 99%

Reversible Inactivation of Nitrate Reductase by NADH and the Occurrence of Partially Inactive Enzyme in the Wheat Leaf

Aryan

Batt²,

Wallace³

1983

Plant Physiol.

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Nitrate reductase from wheat (Tititum aestivum L. cv Bindawarra) leaves is inactivated by pretreatment with NADH, in the absence of nitrate, a 50% loss of activity occurring in 30 minutes at 25C with 10 micromolar NADH. Nitrate (50 micromolar) prevented inactivation by 10 micromolar NADH while cyanide (1 micromolar) markedly enhanced the degree of inactivation.A rapid reactivation of NADH-inactivated nitrate reductase occurred after treatment with 0.3 mlllimolar ferricyanide or exposure to light (230 milliwatts per square centimeter) plus 20 micromolar flavin adenine dinucleotide. When excess NADH was removed, the enzyme was also reactivated by autoxidation. Nitrate did not influence the rate of reactivation.Leaf nitrate reductase, from plants grown for 12 days on 1 milolar nitrate, Isolated in the late photoperiod or dark period, was activated by ferricyanide or light treatment. This suggests that, at these times of the day, the nitrate reductase in the leaves of the low nitrate plants is in a partially inactive state (NADH-inactivated). The nitrate reductase from moisture-stressed plants showed a greater degree of activation after light treatment, and inactive enzyme in them was detected earlier in the photoperiod.

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“…I), has been shown to be nitrate inducible (Cove and Pateman 1969;Beevers and Hageman 1980), light. activated (Packard 1973;Aparicio et al 1976;Martinez et al 1987), and ammonium repressible (Hipkin and Syrett 1977). Additionally, given the high energetic cost of NO:{-and NO, reduction, induction of this metabolic pathway can affect the photosynthetic performance of phytoplankton.…”

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confidence: 99%

Molecular and physiological responses of diatoms to variable levels of irradiance and nitrogen availability: Growth of Skeletonema costatum in simulated upwelling conditions

1992

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Molecular mechanisms that drive metabolic acclimation to environmental shifts have been poorly characterized in phytoplankton. In this laboratory study, the response of light-and N-limited Skeletonema costatum cells to an increase in light and NO, availability was examined. C assimilation was depressed relative to N assimilation early in enrichment, and the photosynthetic quotient (0, : CO,) increased, consistent with the shunting of reducing equivalents from CO, fixation to NO; reduction. The concomitant increase in dark respiration was consistent with the increased energetic demand associated with macromolecular synthesis. The accelerations of N-specific rates of NO,-uptake and nitrate rcductase activity (NRA) over the first 24 h were comparable to observations for coastal upwelling systems. Increases in cell-specific rates of these proccsscs, however, were confined to the first 8 h of enrichment. The abundance of 18s ribosomal ribonucleic acid (rRNA) increased immediately after the environmental shift, followed by increases in levels of NR-specific mRNA that coincided with the acceleration in NO,-assimilation. NRA, however, exhibited a diurnal rhythm that did not correspond to changes in NR protein abundance, suggesting that enzyme activity was also regulated by direct modulation of existing NR protein by light and NO, -availability.

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Blue light photoreactivation of nitrate reductase from green algae and higher plants

Cited by 85 publications

References 16 publications

In Vivo Blue-Light Activation of Chlamydomonas reinhardii Nitrate Reductase

In Vivo Blue-Light Activation of Chlamydomonas reinhardii Nitrate Reductase

Reversible Inactivation of Nitrate Reductase by NADH and the Occurrence of Partially Inactive Enzyme in the Wheat Leaf

Molecular and physiological responses of diatoms to variable levels of irradiance and nitrogen availability: Growth of Skeletonema costatum in simulated upwelling conditions

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