Activation and Oxidation of Acetic Acid-1-C<sup>14</sup> by Cell Free Homogenates of Germinating Peanut Cotyledons

Rebeiz, Constantin A.; Castelfranco, Paul A.; Breidenbach, R. W.

doi:10.1104/pp.40.2.286

Cited by 14 publications

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References 15 publications

(20 reference statements)

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“…Despite its widespread use during the past two decades, little if any information is available on the formation of free acetate in higher plants. In plants, free acetate is rapidly converted to acetyl-CoA by acetyl-CoA synthetase which was first described by Millerd and Bonner (22) and has been further examined by Hiatt (7) and Rebeiz et aL (31), and purified, and its properties studied by Huang and Stumpf (11). Very recently this enzyme has been found to be solely localized in the chloroplast stroma phase of the spinach leaf cell (16), which is also the organelle where fatty acid synthesis takes place (30).…”

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Origin of Acetate in Spinach Leaf Cell

Liedvogel¹,

Stumpf²

1982

Plant Physiol.

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Mitochondria were isolated from spinach (Spinacia oleracea L.) leaves using a Percoli gradient step. The high purity of the organelle fraction is demonstrated by electron microscopy and biochemical parameters. In the matrix space of these mitochondria, a short-chain acyl-coenzyme A hydrolase is present that converts acetyl-c zme A to acetate and coenzyme A with reasonable rates (Ki, 150 micromolar, V,,,, 140 nanomoles acetate formed milligram1 protein hour-'). The enzyme is product inhibited by coenzyme A-sulfhydryl, other thiols are ineffective; however, the disufikdes 5,5'-dithio-bis-(2-nitrobenzoate) and cystamine stimulate the hydrolysis.The possible role of this mitochondrial enzyme as a means of generating free acetate from pyruvate via acetyl-coenzyme A in the mitochondria of mature spinach leaves is discussed. It is suggested that free acetate moves rapidly from the mitochondrion to the chloroplast where acetyl-coenzyme A synthetase, solely localized in this organelle, converts the metabolicaliy inert free acetate to the highly active acetyl-coenzyme A.

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Origin of Acetate in Spinach Leaf Cell

Liedvogel¹,

Stumpf²

1982

Plant Physiol.

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“…The key enzyme here is acetyl thiokinase (Hanvood, 1975~). Preparations from two nonphotosynthetic plant tissues have been examined (Rebeiz, Castelfranco & Breidenbach, 1965 ;Huang & Stumpf, 1970) and the enzyme found to be similar to the yeast enzyme (Berg, 1956). Since preparations of chloroplasts readily utilize exogenous acetate, they must contain active thiokinase which most probably has similar properties.…”

Section: A Origin Of Acetyl Coenzyme Amentioning

confidence: 99%

Biosynthesis of Small Molecules in Chloroplasts of Higher Plants

Givan

Harwood

1976

Biological Reviews

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Summary 1. Chloroplasts of higher plants contain enzymes which permit them to synthesize many kinds of small molecules in addition to carbohydrates. 2. Either aqueous or non‐aqueous techniques may be used to isolate chloroplasts. Aqueous methods permit the isolation of chloroplasts showing high rates of photosynthesis; the organelles can be purified by means of density gradients. Non‐aqueously isolated chloroplasts cannot photosynthesize, but show good retention of low‐molecular‐weight substances and soluble enzymes. 3. Whole cells photoassimilating 14CO2 show considerable formation of 14C‐labelled amino acids and lipids, but isolated chloroplasts exhibit very poor synthesis of amino acids and lipids from 14CO2. 4. Chloroplasts play an important rôle in reducing nitrate to ammonia. There is controversy about the presence in chloroplasts of nitrate reductase and about the mechanism of the light‐dependent reduction of nitrate to nitrite; however, it is generally agreed that non‐cyclic electron transport directly supports reduction of nitrite to ammonia via a chloroplastic nitrite reductase. 5. Chloroplasts actively assimilate inorganic nitrogen into amino acids. The assimilation reaction is either the reductive amination of α‐ketoglutarate to glutamate or the ATP‐dependent conversion of glutamate to glutamine. The enzyme glutamate synthase has recently been found to be present in chloroplasts and may play an important function in nitrogen assimilation. 6. Numerous transaminases (aminotransferases) are present in chloroplasts. 7. The source of α‐keto‐acid precursors of chloroplastic amino acids is unknown. It remains to be established whether chloroplasts import the required keto acids or whether some of them might be generated via an incomplete tricarboxylic‐acid cycle located in the chloroplast. 8. Chloroplasts contain characteristically high levels of mono and digalactosyl diglycerides, sulpholipid and phosphatidyl glycerol. They also have large amounts of polyunsaturated fatty acids. 9. Fatty acids are synthesized by the concerted action of fatty‐acid synthetase, elongases and desaturases. Two pathways have been implicated for the formation of α‐linolenic acid. 10. The galactosyldiglycerides are synthesized by successive galactosylation of diglyceride. The enzymes responsible are probably located in the chloroplastic envelope. 11. The other major chloroplastic acyl lipids (sulpholipid, phosphatidylglycerol and phosphatidylcholine) have not been, as yet, synthesized de novo by means of isolated chloroplast fractions. However, indirect evidence indicates that the first two are probably formed there. 12. Chlorophyllide synthesis involves the formation of δ‐aminolaevulinic acid (δALA) followed by conversion of δALA to protoporphyrin IX, which is then transformed into protochlorophyll. 13. Recent evidence favours the view that δALA synthesis is not mediated by δALA synthetase but by another pathway in which δALA can be derived from α‐ketoglutarate or glutamate. It has not been established whether this pathway is loca...

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“…Recently soluble preparations which are able to catalyze the ,8-oxidation of higher fatty acvl-CoA derivatives were obtained from castor bean endosperm (17) and peanut cotyledons (12,13,14). The possibility that these soluble preparations might be obtained byr damaging the mitochondria during isolation has not been excluded but this appears unlikely in viewv of the mild procedure used, involving low-speed blending in buffers containing hypertonic sucrose.…”

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Respiratory Changes During Seed Germination. Histological Distribution of Respiratory Enzymes and Mobilization of Fat Reserves in Castor Bean Endosperm and Peanut Cotyledons

Castelfranco¹,

Lott²,

Sabar³

1969

Plant Physiol.

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Abstract. Germinating peanut cotyledons and germinating castor bean endosperm have been compared with respect to their rates of fat dissimilation and with respect to the anatomical distribution of respiratory activity. The lipid mobilization is much slower in peanut cotyledons than in castor bean endosperm. Light hais essentially no effect on either system. As germination progresses, the majority of the succinic dehydrogenase and cytochrome oxidase activities become looalized in the vein regions of peanut cotyledons. In the castor bean endosperm these two activities are uniformly distributed throughout the storage parenchyma and increase with germination until the organ becomes soft and visibly senescent.Castor bean endosperm and peanut cotyledons have been used frequently for biochemical studies on the fate of storage fats during germination. Recently soluble preparations which are able to catalyze the ,8-oxidation of higher fatty acvl-CoA derivatives were obtained from castor bean endosperm (17) and peanut cotyledons (12, 13, 14). The possibility that these soluble preparations might be obtained byr damaging the mitochondria during isolation has not been excluded but this appears unlikely in viewv of the mild procedure used, involving low-speed blending in buffers containing hypertonic sucrose. Regardless of the actual localization of these enzymes, it seems probable that the utilization of storage lipids is dependent uipon mitochondrial activity because ATP is required for the activation of fatty acids and because the reduced pyridine and flavin nucleotides formed during the fl-oxidation pathway must be re-oxidized by the mitochondria in order to produce ATP. In resting seeds the mitochondrial activity is extrenmely low. Mitochondrial development has been studied in germinating peanut cotyledons (, 6, 8) and castor bean endosperm (1, 2).

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Activation and Oxidation of Acetic Acid-1-C¹⁴ by Cell Free Homogenates of Germinating Peanut Cotyledons

Cited by 14 publications

References 15 publications

Origin of Acetate in Spinach Leaf Cell

Origin of Acetate in Spinach Leaf Cell

Biosynthesis of Small Molecules in Chloroplasts of Higher Plants

Respiratory Changes During Seed Germination. Histological Distribution of Respiratory Enzymes and Mobilization of Fat Reserves in Castor Bean Endosperm and Peanut Cotyledons

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Activation and Oxidation of Acetic Acid-1-C14 by Cell Free Homogenates of Germinating Peanut Cotyledons

Cited by 14 publications

References 15 publications

Origin of Acetate in Spinach Leaf Cell

Origin of Acetate in Spinach Leaf Cell

Biosynthesis of Small Molecules in Chloroplasts of Higher Plants

Respiratory Changes During Seed Germination. Histological Distribution of Respiratory Enzymes and Mobilization of Fat Reserves in Castor Bean Endosperm and Peanut Cotyledons

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Activation and Oxidation of Acetic Acid-1-C¹⁴ by Cell Free Homogenates of Germinating Peanut Cotyledons