Glutamate synthase ferredoxin dependent

Glutamate synthase (ferredoxin) [EC 1.4.7.1], also known as ferredoxin-dependent glutamate synthase, is an iron-sulfur flavoprotein, that catalyzes the reaction of L-glutamine with a-ketoglutarate (or, 2-oxoglutarate) and two reduced ferredoxin molecules to produce two... 

RESONANCE RAMAN SPECTROSCOPY Ferredoxin-dependent enzymes, ADRENODOXIN BENZENE 1,2-DIOXYGENASE FERREDOXIN NADP REDUCTASE GLUTAMATE SYNTHASE HYDROGENASE... 

The subcellular localization of glutamate synthase has been studied only in angiospcrms and the available evidence indicates that the ferredoxin-dependent enzyme of shoot tissue is restricted to the chloroplasts (Rathnam and Edwards, 1976 Harel et al., 1977 Wallsgrove et al., 1979). This is of course consistent with the electron donor, reduced ferredoxin being restricted to the chloroplasts, and suggests that in other photosynthetic eukaryotes the enzyme is likely to be chloroplastic. 

In contrast the enzyme purified from lupin root nodule cytosol is reported to consist of a single polypeptide chain of molecular weight 235,000 (Boland and Benny, 1977). No information is available at present regarding the possible subunit structure of other eukaryote glutamate synthases although the ferredoxin-dependent enzyme from V. faba has a molecular weight of 150,000, as determined by gel filtration (Wallsgrove et al., 1977) and the pyridine nucleotide-dependent enzyme of Saccharomyces cerevisiae has a sedimentation coefficient of 14.6 S (Roon et al., 1974). 

Shimojima, M. et al. (2005) Ferredoxin-dependent glutamate synthase moonlights in plant sulfolipid biosynthesis by fotming a complex with SQDl. Arch. Biochem. Biophys. 436, 206-214... 

Ferredoxin-dependent glutamate synthase has been purified from bean leaves (Wallsgrove etal., 977), maize (Matoh et al., 1980), rice leaves and roots (Suzuki and Gadal, 1982), Chlamydomonas (Galvan et al., 1984), spinach (Hirasawa and Tamura, 1984), tomato (Avila et al., 1987), and barley (Marquez et al, 1988). Full details of the assay and purification of the enzyme have been described by Lea et al. (1990). 

Antisera to ferredoxin-dependent glutamate synthase have been prepared from protein purified from rice leaves (Suzuki et al., 1982), tomato leaves (Botella et al., 1988), and barley leaves (Marquez et al., 1988). The protein in the green leaves of rice is very similar to that isolated from etiolated tissue but... 

More recently Avila and Wallsgrove (1990) have shown that the antisera raised to barley ferredoxin-dependent glutamate synthase are able to inhibit the enzyme activity isolated from a range of plant sources. However, clear precipitation lines were detected only by Ouchterlony double-difiusion analysis with extracts from barley, wheat, rye, and rice. The enzyme from dicotyledonous and C4 plants appeared to have major differences in the amino acid composition from that purified from barley. 

Compared to the ferredoxin-dependent enzyme, much less is known abut reduced pyridine nucleotide-specific glutamate synthase. There have been earlier reports that the enzyme may use both NADH and NADPH as a coenzyme (Beevers and Storey, 1976 Kang and Titus, 1981 Chiu and Shaigool, 1979). Although there is good evidence that an NADPH-specific form operates in bacteria (Tempest et al., 1970 Yelton and Yoch, 1981), as will be seen below there is little evidence that it plays a role in higher plants. 

In green tissues the enzyme is present in low concentrations compared to the ferredoxin-dependent glutamate synthase (Matoh et al., 1979 Matoh and Ta-kahashi, 1981 Wallsgrove c/a/., 1982 Avillacta/., 1984 Hechter a/., 1988). In mustard cotyledons the enzyme is induced by red light pulses, suggesting a key role for phytochrome. In contrast to the ferredoxin form, the enzyme is induced by nitrate but not depressed by the addition of ammonium ions (Hecht et al., 1988). 

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