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Glyceraldehyde‐3‐phosphate dehydrogenase is regulated by ferredoxin‐ NADP reductase in the diatom A sterionella formosa
Author(s) -
Mekhalfi Malika,
Puppo Carine,
Avilan Luisana,
Lebrun Régine,
Mansuelle Pascal,
Maberly Stephen C.,
Gontero Brigitte
Publication year - 2014
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/nph.12820
Subject(s) - glyceraldehyde 3 phosphate dehydrogenase , dehydrogenase , nicotinamide adenine dinucleotide phosphate , biochemistry , ferredoxin , pentose phosphate pathway , ferredoxin—nadp(+) reductase , biology , reductase , chloroplast , enzyme , glycolysis , oxidase test , gene
Summary Diatoms are a widespread and ecologically important group of heterokont algae that contribute c . 20% to global productivity. Previous work has shown that regulation of their key C alvin cycle enzymes differs from that of the Plantae, and that in crude extracts, glyceraldehyde‐3‐phosphate dehydrogenase ( GAPDH ) can be inhibited by nicotinamide adenine dinucleotide phosphate reduced ( NADPH ) under oxidizing conditions. The freshwater diatom, A sterionella formosa , was studied using enzyme kinetics, chromatography, surface plasmon resonance, mass spectrometry and sequence analysis to determine the mechanism behind this GAPDH inhibition. GAPDH interacted with ferredoxin–nicotinamide adenine dinucleotide phosphate ( NADP ) reductase ( FNR ) from the primary phase of photosynthesis, and the small chloroplast protein, CP 12. Sequences of copurified GAPDH and FNR were highly homologous with published sequences. However, the widespread ternary complex among GAPDH , phosphoribulokinase and CP 12 was absent. Activity measurements under oxidizing conditions showed that NADPH can inhibit GAPDH ‐ CP 12 in the presence of FNR , explaining the earlier observed inhibition within crude extracts. Diatom plastids have a distinctive metabolism, including the lack of the oxidative pentose phosphate pathway, and so cannot produce NADPH in the dark. The observed down‐regulation of GAPDH in the dark may allow NADPH to be rerouted towards other reductive processes contributing to their ecological success.