Elsevier

FEBS Letters

Volume 219, Issue 2, 27 July 1987, Pages 347-350
FEBS Letters

Na+-induced uptake of pyruvate into mesophyll chloroplasts of a C4 plant, Panicum miliaceum

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Abstract

Uptake of [1-14C]pyruvate into the sorbitol-impermeable space of mesophyll chloroplasts of a C4 plant, Panicum miliaceum L., was investigated using a silicone oil filtering centrifugation method. An abrupt change of Na+ concentration in the suspending medium of the chloroplasts in the dark induced accumulation of pyruvate in the stroma, similar to the case of light-driven active uptake. The effect was specific to Na+ among various mono- and divalent cations. The apparent Km for Na+ was in the range 2–5 mM. The Km for pyruvate was about 0.7 mM, which was similar to the value obtained in light-driven uptake. The possible role of Na+ symport in active pyruvate uptake by C4 mesophyll chloroplasts is discussed.

Keywords

Pyruvate transport
Chloroplast membrane
Mesophyll chloroplast
C4 photosynthesis
Na+ jump
(Panicum miliaceum)

Abbreviations

MCp, mesophyll chloroplasts
PEP, phosphoenolpyruvate
Pyr, pyruvate
[Pyr]in, pyruvate concentration in the sorbitol-impermeable space of chloroplasts
[Pyr]ex, pyruvate concentration in the external medium

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