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Titolo:
ADP-GLUCOSE DRIVES STARCH SYNTHESIS IN ISOLATED MAIZE ENDOSPERM AMYLOPLASTS - CHARACTERIZATION OF STARCH SYNTHESIS AND TRANSPORT-PROPERTIESACROSS THE AMYLOPLAST ENVELOPE
Autore:
MOHLMANN T; TJADEN J; HENRICHS G; QUICK WP; HAUSLER R; NEUHAUS HE;
Indirizzi:
UNIV OSNABRUCK,BARBARASTR 11 D-49069 OSNABRUCK GERMANY UNIV OSNABRUCK D-49069 OSNABRUCK GERMANY UNIV SHEFFIELD,DEPT ANIM & PLANT SCI,ROBERT HILL INST SHEFFIELD S10 2UQ S YORKSHIRE ENGLAND UNIV COLOGNE,INST BOT D-50931 COLOGNE GERMANY
Titolo Testata:
Biochemical journal
, volume: 324, anno: 1997,
parte:, 2
pagine: 503 - 509
SICI:
0264-6021(1997)324:<503:ADSSII>2.0.ZU;2-P
Fonte:
ISI
Lingua:
ENG
Soggetto:
HEXOSE-PHOSPHATE TRANSLOCATOR; CAULIFLOWER-BUD AMYLOPLASTS; PEA ROOT PLASTIDS; SPINACH-CHLOROPLASTS; INORGANIC-PHOSPHATE; ADENYLATE TRANSLOCATOR; WHEAT ENDOSPERM; CULTURED-CELLS; HIGHER-PLANTS; GLUCOSE-6-PHOSPHATE;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
46
Recensione:
Indirizzi per estratti:
Citazione:
T. Mohlmann et al., "ADP-GLUCOSE DRIVES STARCH SYNTHESIS IN ISOLATED MAIZE ENDOSPERM AMYLOPLASTS - CHARACTERIZATION OF STARCH SYNTHESIS AND TRANSPORT-PROPERTIESACROSS THE AMYLOPLAST ENVELOPE", Biochemical journal, 324, 1997, pp. 503-509

Abstract

We recently developed a method of purifying amyloplasts from developing maize (Zen mays L.) endosperm tissue [Neuhaus, Them, 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 [C-14]Glc6Por [P-32]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-14]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 starchsynthesis by ATP are discussed with respect to the stromal generationof AMP required for ADPGlc uptake.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 07/04/20 alle ore 23:01:13