Immunofluorescent localization of phosphoenolpyruvate carboxylase and ribulose 1,5-bisphosphate carboxylase/oxygenase proteins in leaves of C3, C4 and C3?C4 intermediate Flaveria species

Planta ◽  
1985 ◽  
Vol 165 (4) ◽  
pp. 439-445 ◽  
Author(s):  
J. E. Reed ◽  
R. Chollet
Keyword(s):  
Phosphoenolpyruvate Carboxylase ◽  
Immunofluorescent Localization ◽  
Bisphosphate Carboxylase ◽  
Flaveria Species

The inorganic carbon requirements for nitrogen assimilation

1991 ◽  
Vol 69 (5) ◽  
pp. 1139-1145 ◽  
Author(s):  
David H. Turpin ◽  
Greg C. Vanlerberghe ◽  
Alan M. Amory ◽  
Robert D. Guy
Keyword(s):  
Amino Acid ◽  
Phosphoenolpyruvate Carboxylase ◽  
Nitrogen Assimilation ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Sufficient Conditions ◽  
Acid Synthesis ◽  
Amino Acid Synthesis ◽  
Bisphosphate Carboxylase ◽  
N Assimilation

In the green alga Selenastrum minutum (Naeg.) Collins the assimilation of NH4+ into the full suite of protein amino acids requires at least three separate and distinct inorganic carbon fixing reactions, catalyzed by the enzymes ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco), phosphoenolpyruvate carboxylase (PEPC), and carbamoyl phosphate synthetase. In this paper we examine the requirements for CO2 fixation of NH4+ assimilation in this organism. When grown under N-sufficient conditions, NH4+ assimilation is directly dependent upon photosynthetic CO2 fixation to provide carbon skeletons for amino acid synthesis. When cultured under N-limited conditions, the cells accumulate starch, which is then available for amino acid synthesis. This alleviates the requirement of photosynthetic CO2 fixation for NH4+ assimilation. N-limited cells, however, still exhibit a nonphotosynthetic CO2 requirement for N assimilation that is mediated through PEPC. This activity of PEPC increases during N assimilation to replenish TCA cycle intermediates consumed during amino acid synthesis. The in vivo activity of this enzyme is tightly regulated so that there are ~0.3 moles C fixed per mole N assimilated. In S. minutum PEPC is regulated primarily by the ratio of glutamine/glutamate, thus providing a mechanism by which primary NH4+ assimilation modulates the supply of carbon for amino acid biosynthesis. Activation of PEPC during NH4+ assimilation occurs in both the light and the dark. Key words: dissolved inorganic carbon, nitrogen assimilation, phosphoenolpyruvate carboxylase, photosynthesis, amino acid synthesis, respiration.

The synthesis of phosphoenolpyruvate carboxylase in imbibing sorghum seeds

1991 ◽  
Vol 69 (2-3) ◽  
pp. 141-145 ◽  
Author(s):  
Eli Khayat ◽  
Erwin B. Dumbroff ◽  
Bernard R. Glick
Keyword(s):  
Enzyme Activity ◽  
Seed Development ◽  
Phosphoenolpyruvate Carboxylase ◽  
Bisphosphate Carboxylase ◽  
Seeds Germination

When sorghum seeds were imbibed either in the light or in the dark, the presence of newly synthesized phosphoenolpyruvate carboxylase (PEPC) could be detected immunologically after approximately 6 h. In addition, both PEPC mRNA and enzyme activity were detected in extracts of dry seeds prior to imbibition. By contrast, ribulose-1,5-bisphosphate carboxylase mRNA, protein, and activity, as well as chlorophyll, were not detected even after 24 h of imbibition. These observations suggest that the nonphotosynthetic form of PEPC is synthesized during seed development and may play an important role in the germinative process.Key words: phosphoenolpyruvate carboxylase, sorghum seeds, germination, ribulose-1,5-bisphosphate carboxylase.

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