Inhibition of chlorophyll biosynthesis by mercury in excised etiolated maize leaf segments during greening: effect of 2-oxoglutarate.
Mercury (0.01-1.0 mM) inhibited chlorophyll formation in greening maize leaf segments. However, supplementing incubation medium with 2-oxoglutarate, maintained substantially higher level of chlorophyll in absence of metal after an initial period of 8 hr. On preincubation of leaf segments with HgCl2, per cent inhibition of chlorophyll synthesis by metal was same in the presence and absence of 2-oxoglutarate. Supply of 2-oxoglutarate (0.1-10.0 mM) exerted concentration dependent effect on chlorophyll formation in absence or presence of metal. Increase in delta-amino levulinic acid dehydratase as well as NADH-glutamate synthase activity and decrease in NADH-glutamate dehydrogenase activity by 2-oxoglutarate in the presence of Hg suggested that glutamate for delta-amino levulinic acid synthesis could be made available from NH4+ assimilation via., glutamine synthetase/glutamate synthase pathway during mercury toxicity.
Jain
Meeta
M
School of Biochemistry, Devi Ahilya University, Takshashila Parisar, Khandwa Road, Indore 452 017, India.
Gadre
Rekha
R
D000622:Aminolevulinic Acid / Q000378:metabolism; D000641:Ammonia / Q000378:metabolism; D002734:Chlorophyll / Q000096:biosynthesis*; D004305:Dose-Response Relationship, Drug; D005970:Glutamate Synthase / Q000378:metabolism; D018698:Glutamic Acid / Q000378:metabolism; D007656:Ketoglutaric Acids / Q000494:pharmacology*; D008027:Light; D008628:Mercury / Q000633:toxicity*; D009243:NAD / Q000378:metabolism; D010788:Photosynthesis; D018515:Plant Leaves / Q000187:drug effects / Q000201:enzymology; D000623:Porphobilinogen Synthase / Q000378:metabolism; D011837:Radiation-Protective Agents / Q000494:pharmacology*; D003313:Zea mays / Q000187:drug effects* / Q000378:metabolism
D007656:Ketoglutaric Acids; D011837:Radiation-Protective Agents; D009243:NAD; D002734:Chlorophyll; D018698:Glutamic Acid; D000641:Ammonia; D000622:Aminolevulinic Acid; D005970:Glutamate Synthase; D000623:Porphobilinogen Synthase; D008628:Mercury