title: Characterization of a light-dependent glutamate synthase activity in Chlamydomonas reinhardtii.
abstract: Photosynthetically active vesicles prepared from Chlamydomonas reinhardtii retained a light-dependent glutamate synthase activity which was highly specific for 2-oxoglutarate (Km=2.1 mM) and L-glutamine (Km=0.9 mM) as amido group acceptor and donor respectively. This activity was inhibited by azaserine, p-hydroxymercuribenzoate and 3-(p-chlorophenyl)-1,1-dimethyl urea.Light-dependent synthesis of glutamate was also obtained by coupling Chlamydomonas photosynthetic particles to purified ferredoxin-glutamate synthase, using ascorbate and 2,6-dichlorophenol-indophenol as electron donor. This system was also specific for 2-oxoglutarate (Km=1 mM) and L-glutamine (Km=0.8 mM) as substrates, and was stimulated by dithioerythritol. Azaserine and p-hydroxymercuribenzoate, but not 3-(p-chlorophenyl)-1,1-dimethyl urea, inhibited the reconstituted activity; high concentrations of 2-oxoglutarate were inhibitory.
authors.affiliation: Departamento de Bioquímica, Facultad de Química, Apartado 553, 41080, Sevilla, Spain.
authors.forename: A J
authors.initials: AJ
authors.lastname: Márquez
authors.forename: M A
authors.initials: MA
authors.lastname: Serra
authors.forename: J M
authors.initials: JM
authors.lastname: Vega