Malate Synthesis in Crassulacean Leaves. I. The Distribution of C14 in Malate of Leaves Exposed to C14O2 in the Dark.

Bradbeer, J. W.; Ranson, S. L.; Stiller, Mary

doi:10.1104/pp.33.1.66

Cited by 78 publications

(31 citation statements)

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“…In higher plants, dark fixation of CO2 although common to all plant organs is more noticeable in plants with thick or succulent leaves (Bradbeer, Ranson and Stiller, 1958;Ranson and Thomas, i960;Saltman et al, 1956;Warburg, 1886). Certain roots (Ting and Dugger, 1965a, b) and mycorrhizas (Harley, 1964) also fix CO2.…”

Section: Introductionmentioning

confidence: 99%

PARTIAL IDENTIFICATION OF DARK ¹⁴CO₂ FIXATION PRODUCTS IN LEAVES OF CATTLEYA (ORCHIDACEAE)

Knauft

Arditti

1969

New Phytologist

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Section: Introductionmentioning

confidence: 99%

PARTIAL IDENTIFICATION OF DARK ¹⁴CO₂ FIXATION PRODUCTS IN LEAVES OF CATTLEYA (ORCHIDACEAE)

Knauft

Arditti

1969

New Phytologist

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“…The oxaloacetic acid produiced can be converted to malic acid by malate dehydrogenase, which was also demonstrable in the leaf extracts. A second carboxylation reaction in the acid-synthesizing pathway was proposed on the basis of the constant labeling of malic acid, produced by leaves in 14CO9 (6). The ratio of radioactivity fotund in carbon-4 to that in carbon-I was constantly 2:1 tunder a great variety of conditions, while the labeling of 1 Present address: Philips Research Laboratories, N. V. Philips' Gloeilamnpenfabrieken, Eindhoven, Netherlands.…”

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confidence: 99%

Temperature Features of Enzymes Affecting Crassulacean acid Metabolism

Brandon

1967

Plant Physiol.

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Summiilary. Enzymes involved in malic acid production via a pathway with 2 carboxylation reactions and in malic acid conversion via total oxidation have been demonstrated in mitochondria of Bryophyllurn tutbiflorumn Harv. Activation of the mitochondria by Tween 40 was necessary to reveal part of the enzyme activities. The temperature behaavior of the enzymes has been investigated, revealing optimal activity of acid-producing enzymes at 350. Even at 530 the optimum for acid-converting enzymes was not yet reached. From the simultaneous action of acid-producing and acid-converting enzyme systems the overall result at different temperatures was estajblished. Up to 150 the net result was a malic acid prodduction. Mloderate temperattures brought about a decrease in this accumulation, which was partly accompanied by a shift to isocitrate production, while at higher temperatures total oxidation of the acids exceeded the production. (21,22,24) and P-enol(pyrtuvate carboxylase has been stuggested as catalyzing the CO., fixatioin. The oxaloacetic acid produiced can be converted to malic acid by malate dehydrogenase, which was also demonstrable in the leaf extracts. A second carboxylation reaction in the acid-synthesizing pathway was proposed on the basis of the constant labeling of malic acid, produced by leaves in 14CO9 (6). The ratio of radioactivity fotund in carbon-4 to that in carbon-I was constantly 2:1 tunder a great variety of conditions, while the labeling of carbon-2 and carbon-3 could never be detected. This was explained by assuming an acid synthesis via carboxylation of ribulose 1,5-di,P to glvcerate 3-P, followed by conversion of glycerate 3-P to P-enolpyruvate, a second carboxylation (resulting in oxaloaceti;c acid) and reduction to malic acid. This pathway implies participation of the oxidative pentose phosphate pathway, so that the following reaction sequence for acid production can be proposed: starch glucose 6-P --ribulose 1,5-diP glycer.ate 3-P P-enolpyruvate -* malate.For acid conversion a role is attributed to the malic enzyme (22,23), which converts malate to pyruvate, followed by total oxidation of this product by the tricarboxylic acid cycle (7,14).That the acid accutmulation is a result of the dominance o-f acid-synthesizing enzymes at low temperatures, while the acid decrease is a consequence of the fact that conversion exceecds production at higher temperatures was demonstrated by Bennet-Clark (3)

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“…Recently this contention gained some support from the observation of labeled 3-PGA after dark CO2 fixation of isolated cells of Sedum telephium (2). Reinvestigating the early reports of Bradbeer et al (3) and Jolchine (6), Sutton and Osmond (10) reported that malate was labeled exclusively in the C-4 position after a short time of CO2 dark fixation in leaves of four CAM species, whereas after longer fixation times label also appeared in the C-1 position. These investigators attributed the formerly observed 2:1 ratio to an erroneous method of malate degradation.…”

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“…Accumulation of malate during darkness in plants exhibiting Crassulacean acid metabolism was suggested in 1958 by Bradbeer et al (3) to occur via two CO2 fixation steps: first, RuDP2 carboxylase was thought to fix CO2 generating two molecules of 3-PGA, which subsequently were converted to PEP; second, this PEP should be subject to a second carboxylation step yielding OAA, finally giving rise to malate. This hypothesis was based upon the finding that label in carbons 4 and 1 in malate was distributed at a constant ratio of 2:1 after short and long periods of dark CO2 fixation.…”

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Equilibration of Label in Malate during Dark Fixation of CO₂ in Kalanchoë fedtschenkoi

Dittrich¹

1976

Plant Physiol.

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In vitro studies of dark 14CO2 fixation with isolated cell aggregates of Kalanchocefedtschenkoi showed that malate synthesized after 20 Bradbeer et al. (3) to occur via two CO2 fixation steps: first, RuDP2 carboxylase was thought to fix CO2 generating two molecules of 3-PGA, which subsequently were converted to PEP; second, this PEP should be subject to a second carboxylation step yielding OAA, finally giving rise to malate. This hypothesis was based upon the finding that label in carbons 4 and 1 in malate was distributed at a constant ratio of 2:1 after short and long periods of dark CO2 fixation. Recently this contention gained some support from the observation of labeled 3-PGA after dark CO2 fixation of isolated cells of Sedum telephium (2). Reinvestigating the early reports of Bradbeer et al. (3) and Jolchine (6), Sutton and Osmond (10) reported that malate was labeled exclusively in the C-4 position after a short time of CO2 dark fixation in leaves of four CAM species, whereas after longer fixation times label also appeared in the C-1 position. These investigators attributed the formerly observed 2:1 ratio to an erroneous method of malate degradation. Additional insight into this matter was provided by in vitro studies of Kluge et al. (7). Upon feeding PEP to tissue slices of two CAM plants during 14CO2 fixation in the dark, the incorporation of 14C was stimulated, but the ratio of label in C-4 to C-1 remained about 7:3, similar to that of the control. This observation was a first indication that the labeling pattern in malate might not be a consequence of carboxylation reactions, but of reactions occurring after carboxylation. This paper presents additional evidence that carboxylation of RuDP is not involved during synthesis of malate in the dark and that label appearing in C-1 of malate is presumably due to the action of fumarase. MATERIALS AND METHODSPlant Material. Mature plants of Kalanchoe fedtschenkoi were kept in an environmental control chamber at a rhythm of 9 hr light (40,000 lux fluorescent tubes plus red light) at 28 C and 40% relative humidity and corresponding 15 hr dark at 17 C and 78% relative humidity. Diurnal changes of acidity in medium size leaves were about 100 ueq/g fresh weight.Selection of Incubation Medium. At the end of the light period, pieces of 2 cm2 were cut out of mature leaves and the epidermis of the lower side was carefully peeled off. These pieces of tissue were floated on water upside down and allowed to take up 14CO2 in the dark for 10 min. After rinsing with distilled H20 for 5 min, the tissue was incubated at 25 C in 5 ml of various solutions, which were renewed each hour. Solution one was distilled H20, solution two contained 50 mm HEPES, pH 7.5, 0.1 mm Ca(NO3)2, 1 mM MgCl2, and 1 mm K2HPO4; solutions three to six contained buffer as solution two plus 0.4, 0.6, 0.8, and 1 M sorbitol, respectively.After 5 hr the leaf tissues were rinsed with distilled H2O and extracted in boiling ethanol. The leakage of radioactivity from the tissues was determined and com...

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Malate Synthesis in Crassulacean Leaves. I. The Distribution of C¹⁴ in Malate of Leaves Exposed to C¹⁴O₂ in the Dark.

Cited by 78 publications

References 13 publications

PARTIAL IDENTIFICATION OF DARK ¹⁴CO₂ FIXATION PRODUCTS IN LEAVES OF CATTLEYA (ORCHIDACEAE)

PARTIAL IDENTIFICATION OF DARK ¹⁴CO₂ FIXATION PRODUCTS IN LEAVES OF CATTLEYA (ORCHIDACEAE)

Temperature Features of Enzymes Affecting Crassulacean acid Metabolism

Equilibration of Label in Malate during Dark Fixation of CO₂ in Kalanchoë fedtschenkoi

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Malate Synthesis in Crassulacean Leaves. I. The Distribution of C14 in Malate of Leaves Exposed to C14O2 in the Dark.

Cited by 78 publications

References 13 publications

PARTIAL IDENTIFICATION OF DARK 14CO2 FIXATION PRODUCTS IN LEAVES OF CATTLEYA (ORCHIDACEAE)

PARTIAL IDENTIFICATION OF DARK 14CO2 FIXATION PRODUCTS IN LEAVES OF CATTLEYA (ORCHIDACEAE)

Temperature Features of Enzymes Affecting Crassulacean acid Metabolism

Equilibration of Label in Malate during Dark Fixation of CO2 in Kalanchoë fedtschenkoi

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Malate Synthesis in Crassulacean Leaves. I. The Distribution of C¹⁴ in Malate of Leaves Exposed to C¹⁴O₂ in the Dark.

PARTIAL IDENTIFICATION OF DARK ¹⁴CO₂ FIXATION PRODUCTS IN LEAVES OF CATTLEYA (ORCHIDACEAE)

PARTIAL IDENTIFICATION OF DARK ¹⁴CO₂ FIXATION PRODUCTS IN LEAVES OF CATTLEYA (ORCHIDACEAE)

Equilibration of Label in Malate during Dark Fixation of CO₂ in Kalanchoë fedtschenkoi