Characterization of a light-dependent glutamate synthase activity inChlamydomonas reinhardtii

✍ Scribed by Antonio J. Márquez; M. Angeles Serra; José M. Vega

• Book ID: 104615204
• Publisher: Springer
• Year: 1987
• Tongue: English
• Weight: 436 KB
• Volume: 12
• Category: Article
• ISSN: 0166-8595
• DOI: 10.1007/bf00019152

✦ Synopsis

Photosynthetically active vesicles prepared from Chlamydomonas reinhardtii retained a light-dependent glutamate synthase activity which was highly specific for 2-oxoglutarate (Kin = 2.1 raM) and L-glutamine (Kin = 0.9 mM) as amido group acceptor and donor respectively. This activity was inhibited by azaserine, p-hydroxymercuribenzoate and 3-(p-chlorophenyl)-l,1dimethyl 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 = l raM) and L-glutamine (K m = 0.8raM) as substrates, and was stimulated by dithioerythritol. Azaserine and p-hydroxymercuribenzoate, but not 3-(p-chlorophenyl)-l,l-dimethyl urea, inhibited the reconstituted activity; high concentrations of 2-oxoglutarate were inhibitory.