Bundle-sheath thylakoids from NADP-malic enzyme-type C4 plants require an exogenous electron donor for enzyme light activation.
Light activation of either NADP-malate dehydrogenase (EC 1.1.1.82) or fructose-1,6-bisphosphate phosphatase (EC 3.1.3.11) was assayed in a reconstituted chloroplastic, system comprising the isolated proteins of the ferredoxin-thioredoxin light-activation system and thylakoids from either mesophyll or bundle-sheath tissues of different C4 plants. While C4-plant thylakoids functionned almost equally well with C3-or C4-plant proteins, the photosyntem-II-deficient bundle-sheath thylakoids from the NADP-malic enzyme type, were unable to perform enzyme photoactivation unless supplemented with an electron donor to photosystem I. Bundle-sheath thylakoids isolated from plants showing no photosystem-II deficiency did not require such an addition. The results are discussed with respect to a possible requirement for a physiological reductant of ferredoxin for enzyme light activation in bundle-sheath, tissues.
Laboratoire de Photosynthèse et Métabolisme, Université de Paris-Sud, Centre d'Orsay, Bât. 430, F-91405, Orsay-Cedex, France.
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D
Lavergne
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M
Droux
J P
JP
Jacquot
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M
Miginiac-Maslow
M L
ML
Champigny
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P
Gadal