Specific transport of inorganic phosphate, glucose 6‐phosphate, dihydroxyacetone phosphate and 3‐phosphoglycerate into amyloplasts from pea roots

Borchert, Sieglinde; Grosse, Heike; Heldt, Hans W.

doi:10.1016/0014-5793(89)80955-x

Cited by 104 publications

(51 citation statements)

References 17 publications

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“…1). In this respect, these chloroplasts are similar to heterotrophic plastids purified from pea roots (Bowsher et al, 1989;Borchert et al, 1993), soybean cell-suspension cultures (Coates and ap Rees, 1993)' and developing wheat endosperm (Tetlow et al, 1994). The observation that 1 mM Glc-6-P in the incubation medium induces near-maximal rates of decarboxylation ( Fig.…”

Section: Discussionmentioning

confidence: 60%

“…From back-exchange experiments using 32Pi-preloaded chloroplasts from these fruits, it is evident that these plastids contain a transport system mediating the counter-exchange of phosphorylated intermediates (Table I). Obviously, this translocator possesses transport characteristics similar to those of the Glc-6-P translocator found in pea root plastids (Borchert et al, 1989) and amyloplasts purified from cauliflower buds (Mohlmann et al, 1095). In contrast to chloroplasts purified 'from spinach leaves, which are unable to transport Glc-6-P via the phosphate translocator (Fliege et al, 1978) (Table I), chloroplasts from green pepper fruits use Glc-6-P as a transport substrate with around 70% of the transport efficiency that i:; found for Pi (Table I).…”

Section: Discussionmentioning

confidence: 72%

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Oxidation of Imported or Endogenous Carbohydrates by Isolated Chloroplasts from Green Pepper Fruits

Thom

Neuhaus

1995

Plant Physiol.

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Pf I a n ze n p h y s i o I og i e, F B 5 B i o I og i e/C h e m i e, U n i ve rs i t a t Os n a b r O c k, D -4 9 O 6 9 Os n a b r ü c k , C e r m a n y Recently, we demonstrated that intact chloroplasts isolated from green pepper (Capsicum annum L.) fruits use exogenous glucose-6-phosphate (Clc-6-P) as the most efficient precursor for starch biosynthesis (O. Batz, R. Scheibe, H.E. Neuhaus [1995] Planta 196: 50-57). Here we demonstrate that these chloroplasts transport this hexose phosphate in counter-exchange for orthophosphate. By measuring the release of 14C0, from [l -'4ClGlc-6-P, we show that isolated fruit chloroplasts also use exogenous Clc-6-P as a substrate for the oxidative pentose-phosphate pathway. l h e rate of decarboxylation appears to be linear with time and is significantly reduced i n the presence of Triton X-100, indicating that the reaction is dependent on plastid integrity. Pyruvate has been identified as a positive effector for flux through the oxidative pentose-phosphate pathway.However, the highest rates of Glc-6-P-driven oxidative pentosephosphate pathway activity are achieved i n the presence of nitrite, 2-oxoglutarate, and glutamine, indicating a strong interaction between nitrogen metabolism and this pathway. I n addition, we show that carbohydrates liberated during starch mobilization are used as substrates for the oxidative pentose-phosphate pathway. Orthophosphate was found to act as an activator for the observed 14C02 release from carbohydrates formerly bound as starch. In this context, we demonstrate that exogenous Clc-6-P competes with endogenous carbohydrates. A possible interaction between exogenous and endogenous carbohydrates is discussed with respect t o altered levels of carbohydrates during fruit development.

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Section: Discussionmentioning

confidence: 60%

Section: Discussionmentioning

confidence: 72%

Oxidation of Imported or Endogenous Carbohydrates by Isolated Chloroplasts from Green Pepper Fruits

Thom

Neuhaus

1995

Plant Physiol.

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“…In contrast with leaf mesophyll chloroplasts [21], most heterotrophic plastids are able to transport hexose phosphates across the inner envelope membrane [20,22]. However, there is a debate about the molecular nature of hexose phosphates imported into heterotrophic plastids and utilized for anabolic reactions.…”

Section: Transport Of Glc6p P I and Other Phosphorylated Intermediatmentioning

confidence: 99%

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

Möhlmann

Tjaden

Henrichs

et al. 1997

Biochemical Journal

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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][396][397][398][399][400][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 ["%C]Glc6P or [$#P]P i in counter exchange with P i , 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 ["%C]ADPGlc, reaching a maximum at

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“…Another possibility is that AGPase activity may be responding to changes in plastid 3PGA/Pi ratio caused by changes in the activity of the envelope triose phosphate:phosphate translocator. This transporter is required to transmit changes of the 3PGA/Pi ratio from one compartment to the other (Borchert et al, 1989;Schott et al, 1995) (Figure 1).…”

Section: Introductionmentioning

confidence: 99%

Starch Synthesis in Potato Tubers Is Regulated by Post-Translational Redox Modification of ADP-Glucose Pyrophosphorylase

et al. 2002

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Transcriptional and allosteric regulation of ADP-Glc pyrophosphorylase (AGPase) plays a major role in the regulation of starch synthesis. Analysis of the response after detachment of growing potato tubers from the mother plant revealed that this concept requires extension. Starch synthesis was inhibited within 24 h of tuber detachment, even though the catalytic subunit of AGPase (AGPB) and overall AGPase activity remained high, the substrates ATP and Glc-1-P increased, and the glycerate-3-phosphate/inorganic orthophosphate (the allosteric activator and inhibitor, respectively) ratio increased. This inhibition was abolished in transformants in which a bacterial AGPase replaced the potato AGPase. Measurements of the subcellular levels of each metabolite between Suc and starch established AGPase as the only step whose substrates increase and mass action ratio decreases after detachment of wild-type tubers. Separation of extracts on nonreducing SDS gels revealed that AGPB is present as a mixture of monomers and dimers in growing tubers and becomes dimerized completely in detached tubers. Dimerization led to inactivation of the enzyme as a result of a marked decrease of the substrate affinity and sensitivity to allosteric effectors. Dimerization could be reversed and AGPase reactivated in vitro by incubating extracts with DTT. Incubation of tuber slices with DTT or high Suc levels reduced dimerization, increased AGPase activation, and stimulated starch synthesis in vivo. In intact tubers, the Suc content correlated strongly with AGPase activation across a range of treatments, including tuber detachment, aging of the mother plant, heterologous overexpression of Suc phosphorylase, and antisense inhibition of endogenous AGPase activity. Furthermore, activation of AGPase resulted in a stimulation of starch synthesis and decreased levels of glycolytic intermediates.

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Specific transport of inorganic phosphate, glucose 6‐phosphate, dihydroxyacetone phosphate and 3‐phosphoglycerate into amyloplasts from pea roots

Cited by 104 publications

References 17 publications

Oxidation of Imported or Endogenous Carbohydrates by Isolated Chloroplasts from Green Pepper Fruits

Oxidation of Imported or Endogenous Carbohydrates by Isolated Chloroplasts from Green Pepper Fruits

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

Starch Synthesis in Potato Tubers Is Regulated by Post-Translational Redox Modification of ADP-Glucose Pyrophosphorylase

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