scholarly journals Effects of the Relative Extrachloroplastic Concentrations of Inorganic Phosphate, 3-Phosphoglycerate, and Dihydroxyacetone Phosphate on the Rate of Starch Synthesis in Isolated Spinach Chloroplasts

1982 ◽  
Vol 70 (2) ◽  
pp. 393-396 ◽  
Author(s):  
Archie R. Portis
Keyword(s):  
Inorganic Phosphate ◽  
Starch Synthesis ◽  
Dihydroxyacetone Phosphate ◽  
Spinach Chloroplasts

HYDROLYSIS OF LECITHIN BY PLANT PLASTID ENZYMES

1955 ◽  
Vol 33 (1) ◽  
pp. 575-589 ◽  
Author(s):  
Morris Kates
Keyword(s):  
Phosphatidic Acid ◽  
Inorganic Phosphate ◽  
Organic Phosphate ◽  
Water Soluble ◽  
Lag Phase ◽  
Carrot Root ◽  
First Order ◽  
Spinach Chloroplasts ◽  
Egg Lecithin ◽  
Hydrolysis Of

Enzymatic liberation of choline from egg lecithin by plastid fractions from sugar beet, spinach, and cabbage leaves and from carrot root was a rapid, first order reaction (up to 70% hydrolysis), and was not preceded by a lag phase. None of the choline-containing products of lecithin degradation (lysolecithin, glycerylphosphorylcholine, or phosphorylcholine) lost choline on incubation with spinach chloroplasts. Inorganic phosphate liberation from lecithin by the plastids was preceded by a lag phase and was much slower than choline liberation. Spinach chloroplasts catalyzed the liberation of inorganic phosphate from L-α-phosphatidic acid and from L-α-glycerophosphate. The water-soluble organic phosphate liberated from lecithin by spinach chloroplasts was identified chromatographically as phosphorylcholine. The ether-soluble organic phosphate produced during the hydrolysis of egg lecithin by carrot plastids was isolated and identified as L-α-phosphatidic acid. These observations suggest that the enzymatic hydrolysis of lecithin by plant plastids involves the following reactions: (1) lecithin → L-α-phosphatidic acid + choline; (2) L-α-phosphatidic acid → inorganic phosphate + diglyceride and/or (3) L-α-phosphatidic acid → glycerophosphate + fatty acids and (4) glycerophosphate → inorganic phosphate + glycerol; and (5) lecithin → phosphorylcholine + diglyceride. The L-α-structure for egg lecithin was confirmed.

scholarly journals Effects of Inorganic Phosphate on the Light Dependent Thylakoid Energization of Intact Spinach Chloroplasts

1989 ◽  
Vol 91 (1) ◽  
pp. 221-226 ◽  
Author(s):  
Dieter Heineke ◽  
Mark Stitt ◽  
Hans W. Heldt
Keyword(s):  
Inorganic Phosphate ◽  
Spinach Chloroplasts

scholarly journals Reconstitution of the hexose phosphate translocator from the envelope membranes of wheat endosperm amyloplasts

1996 ◽  
Vol 319 (3) ◽  
pp. 717-723 ◽  
Author(s):  
Ian J TETLOW ◽  
Caroline G BOWSHER ◽  
Michael J EMES
Keyword(s):  
Inorganic Phosphate ◽  
Competitive Inhibitor ◽  
Dihydroxyacetone Phosphate ◽  
Carrier Protein ◽  
Sugar Phosphate ◽  
Wheat Endosperm ◽  
Single Carrier ◽  
Phosphate Translocator ◽  
Envelope Membranes ◽  
Hexose Phosphates

Amyloplasts were isolated and purified from wheat endosperm and the envelope membranes reconstituted into liposomes. Envelope membranes were solubilized in n-octyl β-D-glucopyranoside and mixed with liposomes supplemented with 5.6 mol% cholesterol to produce proteoliposomes of defined size, which showed negligible leakage of internal substrates. Transport experiments with proteoliposomes revealed a counter-exchange of glucose 1-phosphate (Glc1P), glucose 6-phosphate (Glc6P), inorganic phosphate (Pi), 3-phosphoglycerate and dihydroxyacetone phosphate. The Glc1P/Pi counter-exchange reaction exhibited an apparent Km for Glc1P of 0.4 mM. Glc6P was a competitive inhibitor of Glc1P transport (Ki 0.8 mM), and the two hexose phosphates could exchange with each other, indicating the operation of a single carrier protein. Glc1P/Pi antiport in proteoliposomes showed an exchange stoichiometry at pH 8.0 of 1 mol of phosphate transported per mol of sugar phosphate.

ENZYMIC ACTIVITIES OF SUBCELLULAR PARTICLES FROM LEAVES: IV. PHOTOSYNTHETIC PHOSPHORYLATION AND PHOTOSYNTHESIS BY ISOLATED CHLOROPLASTS FROM PEA LEAVES

1959 ◽  
Vol 37 (6) ◽  
pp. 1217-1225 ◽  
Author(s):  
R. M. Smillie ◽  
G. Krotkov
Keyword(s):  
Carbon Dioxide ◽  
Inorganic Phosphate ◽  
Fixed Carbon ◽  
Spinach Chloroplasts ◽  
Green Pea ◽  
Isolated Chloroplasts

Chloroplasts were isolated in 0.35 M NaCl from green pea leaves. Such preparations formed ATP photosyathetically from AMP or ADP and inorganic phosphate. The conditions and cofactors of this reaction were studied. The rates of photosynthetic phosphorylation by isolated pea chloroplasts were compared with photosynthetic phosphorylation by spinach chloroplasts and with photosynthesis by intact pea leaves. The isolated pea chloroplasts also photosynthetically fixed carbon dioxide. The possible roles of chloroplasts and mitochondria in cellular phosphorylations are discussed.

scholarly journals Peroxisomal localization of glucose-6-phosphate dehydrogenase and pyrophosphate-stimulated dihydroxyacetone-phosphate acyltransferase in mouse kidney

1987 ◽  
Vol 244 (2) ◽  
pp. 443-448 ◽  
Author(s):  
B N Patel ◽  
M I Mackness ◽  
M J Connock
Keyword(s):  
Subcellular Localization ◽  
Dehydrogenase Activity ◽  
Inorganic Phosphate ◽  
Density Gradient Centrifugation ◽  
Gradient Centrifugation ◽  
Mouse Kidney ◽  
Dihydroxyacetone Phosphate ◽  
Ph Optimum ◽  
Dependent Activity ◽  
Glucose 6 Phosphate Dehydrogenase

1. The subcellular localization of dihydroxyacetone-phosphate acyltransferase (DHAPAT) (assayed in the presence of pyrophosphate) and glucose-6-phosphate dehydrogenase (NADP+-dependent) activity in mouse kidney was investigated by density-gradient centrifugation. 2. DHAPAT has a predominantly peroxisomal distribution, and the activity in purified peroxisomes is stimulated by various organic and inorganic phosphate-containing compounds. The pH optimum is acid. 3. Approx. 10% of the cellular NADP+-dependent glucose-6-phosphate dehydrogenase activity is associated with peroxisomal fractions and may provide a source of NADPH for the peroxisomal reduction of acyl-dihydroxyacetone phosphate formed by DHAPAT activity.

scholarly journals ADP-glucose drives starch synthesis in isolated maize endosperm amyloplasts: characterization of starch synthesis and transport properties across the amyloplast envelope

1997 ◽  
Vol 324 (2) ◽  
pp. 503-509 ◽  
Author(s):  
Torsten MÖHLMANN ◽  
Joachim TJADEN ◽  
Gundrun HENRICHS ◽  
Paul W. QUICK ◽  
Rainer HÄUSLER ◽  
...  
Keyword(s):  
Starch Synthesis ◽  
Dihydroxyacetone Phosphate ◽  
Maize Endosperm ◽  
Endosperm Tissue ◽  
Plastid Envelope ◽  
Phosphorylated Compounds ◽  
Saturation Kinetics ◽  
Uptake Data ◽  
Hexose Phosphates

We recently developed a method of purifying amyloplasts from developing maize (Zea mays L.) endosperm tissue [Neuhaus, Thom, Batz and Scheibe (1993) Biochem. J. 296, 395–401]. In the present paper we analyse how glucose 6-phosphate (Glc6P) and other phosphorylated compounds enter the plastid compartment. Using a proteoliposome system in which the plastid envelope membrane proteins are functionally reconstituted, we demonstrate that this type of plastid is able to transport [14C]Glc6P or [32P]Pi in counter exchange with Pi, Glc6P, dihydroxyacetone phosphate and phosphoenolpyruvate. Glucose 1-phosphate, fructose 6-phosphate and ribose 5-phosphate do not act as substrates for counter exchange. Besides hexose phosphates, ADP-glucose (ADPGlc) also acts as a substrate for starch synthesis in isolated maize endosperm amyloplasts. This process exhibits saturation kinetics with increasing concentrations of exogenously supplied [14C]ADPGlc, reaching a maximum at 2 mM. Ultrasonication of isolated amyloplasts greatly reduces the rate of ADPGlc-dependent starch synthesis, indicating that the process is dependent on the intactness of the organelles. The plastid ATP/ADP transporter is not responsible for ADPGlc uptake. Data are presented that indicate that ADPGlc is transported by another translocator in counter exchange with AMP. To analyse the physiology of starch synthesis in more detail, we examined how Glc6P- and ADPGlc-dependent starch synthesis in isolated maize endosperm amyloplasts interact. Glc6P-dependent starch synthesis is not inhibited by increasing concentrations of ADPGlc. In contrast, the rate of ADPGlc-dependent starch synthesis is reduced by increasing concentrations of ATP necessary for Glc6P-dependent starch synthesis. The possible modes of inhibition of ADPGlc-dependent starch synthesis by ATP are discussed with respect to the stromal generation of AMP required for ADPGlc uptake.

HYDROLYSIS OF LECITHIN BY PLANT PLASTID ENZYMES

1955 ◽  
Vol 33 (4) ◽  
pp. 575-589 ◽  
Author(s):  
Morris Kates
Keyword(s):  
Phosphatidic Acid ◽  
Inorganic Phosphate ◽  
Organic Phosphate ◽  
Water Soluble ◽  
Lag Phase ◽  
Carrot Root ◽  
First Order ◽  
Spinach Chloroplasts ◽  
Egg Lecithin ◽  
Hydrolysis Of

Enzymatic liberation of choline from egg lecithin by plastid fractions from sugar beet, spinach, and cabbage leaves and from carrot root was a rapid, first order reaction (up to 70% hydrolysis), and was not preceded by a lag phase. None of the choline-containing products of lecithin degradation (lysolecithin, glycerylphosphorylcholine, or phosphorylcholine) lost choline on incubation with spinach chloroplasts. Inorganic phosphate liberation from lecithin by the plastids was preceded by a lag phase and was much slower than choline liberation. Spinach chloroplasts catalyzed the liberation of inorganic phosphate from L-α-phosphatidic acid and from L-α-glycerophosphate. The water-soluble organic phosphate liberated from lecithin by spinach chloroplasts was identified chromatographically as phosphorylcholine. The ether-soluble organic phosphate produced during the hydrolysis of egg lecithin by carrot plastids was isolated and identified as L-α-phosphatidic acid. These observations suggest that the enzymatic hydrolysis of lecithin by plant plastids involves the following reactions: (1) lecithin → L-α-phosphatidic acid + choline; (2) L-α-phosphatidic acid → inorganic phosphate + diglyceride and/or (3) L-α-phosphatidic acid → glycerophosphate + fatty acids and (4) glycerophosphate → inorganic phosphate + glycerol; and (5) lecithin → phosphorylcholine + diglyceride. The L-α-structure for egg lecithin was confirmed.

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