Photosynthesis and carbon metabolism in a chloroplast preparation fromAcetabularia

Shephard, David C.; Bidwell, R. G. S.

doi:10.1007/bf01279127

Cited by 24 publications

(11 citation statements)

References 18 publications

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“…These preparations differ from higher plant plastids in their unusual stability as shown by their resistance to detergents and their intactness even after long-time storage. Similar results with plastids from siphonous algae were obtained by Shephard and Bidwell (15) and Schonfeldt et al (13).…”

supporting

confidence: 87%

Photosynthetic Properties of Chloroplasts from Chlamydomonas reinhardii

Klein

Chen²,

Gibbs³

1983

Plant Physiol.

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Chloroplasts isolated from synchronous cultures of the unicellular green alga Chamydwnomoan reiri4 Most of the knowledge about the intact plastid originates from studies on higher plant chloroplasts (e.g. spinach, peas). Plastids from sources other than higher plants are either difficult to isolate or it is not easy to obtain the plant material. Therefore, only a few investigations with plastids from other sources are reported in the literature: Grant et aL (4) and Wright and Grant (16) describe some properties of chloroplasts from siphonous marine algae. These preparations differ from higher plant plastids in their unusual stability as shown by their resistance to detergents and their intactness even after long-time storage. Similar results with plastids from siphonous algae were obtained by Shephard and Bidwell (15) and Schonfeldt et al. (13).Recently, chloroplasts could also be isolated from unicellular algae. Intact C02-fixing and protein-synthesizing chloroplasts were purified from Euglena gracilis by Ortiz et al. (12). These plastids apparently lack a phosphate translocator (14), a protein associated with the envelope of higher plant chloroplasts (5).Kombrink and Wober (9) obtained chloroplasts from the unicellular green alga Dunaliella marina by chemical lysis of the cells' membrane. This preparation did not fix CO2 in vitro indicating '

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supporting

confidence: 87%

Photosynthetic Properties of Chloroplasts from Chlamydomonas reinhardii

Klein

Chen²,

Gibbs³

1983

Plant Physiol.

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“…These low saturating light intensities are approximately one tenth of those required for optimum carbon fixation by isolated Spinacia chloroplasts (Jensen and Bassham, 1966), and could be easily maintained in the laboratory for long incubation periods. Isolated Codium vermilara (Schonfeld et al, 1973) and Acetabularia mediterranea (Shephard and Bidwell, 1973) chloroplasts show similar light requirements to those of Codium fragile, and may represent an adaptation of siphonaceous algal chloroplasts to their submarine environment.…”

Section: Conditions For Optimum Rates Of Carbon Fixation By Isolated mentioning

confidence: 97%

THE CARBON FIXATION CHARACTERISTICS OF ISOLATED CODIUM FRAGILE CHLOROPLASTS. CHLOROPLAST INTACTNESS, THE EFFECT OF PHOTOSYNTHETIC CARBON REDUCTION CYCLE INTERMEDIATES AND THE REGULATION OF RuBP⁺ CARBOXYLASE IN VITRO

Cobb

Rott

1978

New Phytologist

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SUMMARYChloroplasts of the siphonaceous marine alga Codium fragile exhibit different carbon fixation characteristics in vitro from those of higher plants. A simple extraction medium, 0.8 M osmoticum and a saturating light intensity of 25 W.m~^ produced maximum rates of 40-60 jumoles CO2 fixed mg. chlorophyll"^ h~^ at 20 C, depending on the age and condition of the parent tissue. No marked lag phase was apparent and fixation proceeded at a linear rate for up to 60 min.Incubation with 10 mM PGA enhanced the fixation rate, as did 10 mM SBP, 10 mM FBP and 5 mM R5P to a lesser extent, whereas 6 PGlu, S7P, F6P, Ru5P and PEP produced no measureable effect. This lack of marked response to the addition of exogenous photosynthetic intermediates is correlated to a lack of induction by these chloroplasts.Using the retention of the soluble stromal enzyme RuBP carboxylase as a criterion of intactness, freshly isolated C. fragile chloroplasts were approximately 80% intact, and were still 40% intact after 96 h storage in the dark on ice.RuBP carboxylase was shown to resemble the higher plant carboxylase, existing in either an active or inactive form depending on the prevailing levels of RuBP and Mg^"^, and to be metabolically regulated by PGA, 6PGlu, SBP, FBP and Pi. Maximum rates obtained with a chloroplast extract were 155 jumoles CO2 fixed mg chlorophyll"^ h"\ at 20°C. Abbreviations

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“…Chloroplasts from Caulerpa cactoides (6), Codium fragile (19), and C. sinpliciuscula all have in common a greater resistance to dissolution in detergent than higher plant chloroplasts, properties which appear to be related to a more complex membrane structure surrounding the chloroplasts (21). Second, the major products of photosynthetic "CO2 fixation in C. simplpcwsc which include alanine, sucrose, and hexose monophosphates resemble the wider array of metabolic products found in chloroplasts from Acetabularia (17). This is in contrast to chloroplasts from higher plants where the range of products is more restricted and triose phosphates are major products (3).…”

Section: Discussionmentioning

confidence: 99%

“…In this they resemble the chloroplasts isolated from Acetabularia where a similar range of products is synthesized by the isolated organelle (17). In this paper the studies of the metabolic competence of chloroplasts from siphonous green algae are extended to include the pathways of assimilation of ammonium into amino acids.…”

mentioning

confidence: 99%

Glutamine Synthetase/Glutamine: α-Ketoglutarate Aminotransferase in Chloroplasts from the Marine Alga Caulerpa simpliciuscula

McKenzie¹,

Ch'Ng²,

Gayler³

1979

Plant Physiol.

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The enzymic capacities for ammonia assimilation into amino acids have been investigated in chloroplasts from the siphonous green alga Caulerpa simpliciuscula (Turner) C. Ag. The results show that these chloroplasts differ from those of higher plants in having present simultaneously the enzymic capacities to permit assimilation of ammonia by two pathways.Glutamine synthetase (EC 6.3.1.2) activity at levels up to 4 jumoles per mg chlorophyll per hour were found in soluble extracts of the chloroplasts. Glutamine(amide):a-ketoglutarate aminotransferase (oxidoreductase ferredoxin) (EC 1.4.7.1) activity at levels up to 1.4 pmoles per mg chlorophyll per hour was detected by incubation of photosynthetically active chloroplasts either in light or with reduced ferredoxin. Together these enzymes provide the capacity for the conventional pathway of ammonium assimilation in chloroplasts via glutamine. A similar level of a glutamate dehydrogenase with an unusually low Km for ammonia which has been described previously in these chloroplasts provides the second potential pathway.Chloroplasts isolated from siphonous green algae have been shown recently to synthesize a different, and often wider, array of photosynthetic products from ''CO2 than higher plant chloroplasts (7,19). In this they resemble the chloroplasts isolated from Acetabularia where a similar range of products is synthesized by the isolated organelle (17). In this paper the studies of the metabolic competence of chloroplasts from siphonous green algae are extended to include the pathways of assimilation of ammonium into amino acids.In chloroplasts of higher plants ammonium is incorporated into amino acids via the two enzymic steps, glutamine synthetase (EC 6.3.1.2) followed by GOGAT2 (Jo). It has been suggested that the situation in chloroplasts isolated from the marine alga Caulerpa simpliciuscula is different, since they have been found to contain high levels of an NADP-dependent glutamate dehydrogenase, with an abnormally low apparent Km for ammonia of 0.4 to 0.7 mM (5). This enzyme could provide an alternative means of ammonium incorporation into amino acids in these algae.GOGAT activity has been demonstrated both in photosynthetic organisms which are more advanced in evolution than C. simpliciuscula and also in those which are more primitive (10, 11). We would expect that GOGAT activity should also be present in C. simpliciuscula unless this species represents a radical departure in evolution from other members of the plant kingdom. Here, we show that the chloroplasts of this siphonous green alga contain the enzymic capacities for both pathways of ammonium assimilation into amino acids. MATERIALS AND METHODSPlant Material. C. simpliciuscula plants were gathered at a depth of 1 to 2 m from the sea at Williamstown, Victoria and held in an illuminated tank of aerated and recirculating seawater on a 12-h light/12-h dark cycle at 16 C.Chloroplast Isolation. The chloroplast fraction was prepared from fronds of C. simpliciuscula by the method described prev...

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Photosynthesis and carbon metabolism in a chloroplast preparation fromAcetabularia

Cited by 24 publications

References 18 publications

Photosynthetic Properties of Chloroplasts from Chlamydomonas reinhardii

Photosynthetic Properties of Chloroplasts from Chlamydomonas reinhardii

THE CARBON FIXATION CHARACTERISTICS OF ISOLATED CODIUM FRAGILE CHLOROPLASTS. CHLOROPLAST INTACTNESS, THE EFFECT OF PHOTOSYNTHETIC CARBON REDUCTION CYCLE INTERMEDIATES AND THE REGULATION OF RuBP⁺ CARBOXYLASE IN VITRO

Glutamine Synthetase/Glutamine: α-Ketoglutarate Aminotransferase in Chloroplasts from the Marine Alga Caulerpa simpliciuscula

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Photosynthesis and carbon metabolism in a chloroplast preparation fromAcetabularia

Cited by 24 publications

References 18 publications

Photosynthetic Properties of Chloroplasts from Chlamydomonas reinhardii

Photosynthetic Properties of Chloroplasts from Chlamydomonas reinhardii

THE CARBON FIXATION CHARACTERISTICS OF ISOLATED CODIUM FRAGILE CHLOROPLASTS. CHLOROPLAST INTACTNESS, THE EFFECT OF PHOTOSYNTHETIC CARBON REDUCTION CYCLE INTERMEDIATES AND THE REGULATION OF RuBP+ CARBOXYLASE IN VITRO

Glutamine Synthetase/Glutamine: α-Ketoglutarate Aminotransferase in Chloroplasts from the Marine Alga Caulerpa simpliciuscula

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THE CARBON FIXATION CHARACTERISTICS OF ISOLATED CODIUM FRAGILE CHLOROPLASTS. CHLOROPLAST INTACTNESS, THE EFFECT OF PHOTOSYNTHETIC CARBON REDUCTION CYCLE INTERMEDIATES AND THE REGULATION OF RuBP⁺ CARBOXYLASE IN VITRO