期刊
EUROPEAN JOURNAL OF PHYCOLOGY
卷 47, 期 3, 页码 207-215出版社
TAYLOR & FRANCIS LTD
DOI: 10.1080/09670262.2012.687459
关键词
Asterionella formosa; Bacillariophyceae; Calvin cycle; Chlamydomonas reinhardtii; Chlorophyta; chromalveolates; CP12; enzyme regulation; Eustigmatophyceae; GAPDH; Plantae; regulation by pH
资金
- Programme Interdisciplinaire Energie PIE, CNRS [PR09-2.2.3-1]
- Agence Nationale de la Recherche [ANR-09-CP2D-06-01, ANR SPINFOLD 09-BLAN-0100]
- Centre National de la Recherche Scientifique (CNRS)
- Aix-Marseille University
- Natural Environment Research Council [ceh010022] Funding Source: researchfish
The regulation of NADPH-dependent GAPDH was analysed in the chromalveolate (eustigmatophyte) Pseudocharaciopsis ovalis and compared with the well-studied chlorophyte Chlamydomonas reinhardtii and with another chromalveolate (diatom), Asterionella formosa. Optimal pH for GAPDH activity in P. ovalis and C. reinhardtii ranged between 8 and 9, but in A. formosa ranged between 6.2 and 8.1. Assuming dark pH values of about 7 in the plastids of all three species, GAPDH would be down-regulated in the dark in C. reinhardtii and P. ovalis, but fully active in A. formosa. The time required for half-maximal GAPDH activity on transfer to reducing conditions, was significantly different in each species: 1.4, 4.0 and 5.9 min in A. formosa, P. ovalis and C. reinhardtii respectively. Under oxidized conditions in P. ovalis and A. formosa, NADPH caused a large inhibition in GAPDH activity even at very low concentrations (10 to 20 mu M) unlike in C. reinhardtii. This inhibition was relieved by addition of a reducing agent suggesting that NADPH can control GAPDH activity under dark-light transitions. A small increase of GAPDH activity with NADP at concentrations higher than 0.5 mM was observed with P. ovalis and C. reinhardtii, while a greater than 1.5-fold stimulation was observed in A. formosa. Regulation of GAPDH in P. ovalis was intermediate between the diatom and the chlorophyte and the possible evolutionary reasons for this are discussed.
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