Multiple Forms of Plant Phosphoenolpyruvate Carboxylase Associated with Different Metabolic Pathways 1
AUTOR(ES)
Ting, Irwin P.
RESUMO
The physical and kinetic properties of multiple forms of phosphoenolpyruvate carboxylase were studied in leaves of C4 and C3 species, their F1 and F3 hybrids, in greening maize leaves, in Crassulacean acid metabolism plants, and in nongreen root tissues. Four different forms are suggested: a C4 photosynthetic phosphoenolpyruvate carboxylase with high Km for phosphoenolpyruvate (∼0.59 mm), Km Mg (∼0.5 mm), and Vmax (∼29 micromoles per minute per milligram of chlorophyll); a C3 photosynthetic phosphoenolpyruvate carboxylase with low Km for phosphoenolpyruvate (∼0.14 mm), Km for Mg (∼0.097 mm), and Vmax (1.5); a Crassulacean acid metabolism type with low Km for phosphoenolpyruvate (0.14 mm), and high Vmax (14 micromoles per minute per milligram of chlorophyll); and a nongreen or nonautotrophic type with low Km for phosphoenolpyruvate, Km for Mg, and low Vmax. In closely related species or within species, the types can be differentiated by anion exchange column chromatography. Each of the four forms is associated with a different metabolic pathway: the phosphoenolpyruvate carboxylase of C4 species for malate generation as a photosynthetic intermediate, the phosphoenolpyruvate carboxylase of C3 species in malate generation as a photosynthetic product, the phosphoenolpyruvate carboxylase of Crassulacean acid metabolism species in malate generation as a CO2 donor for photosynthesis during the subsequent light period, and a nongreen or root type producing malate for ionic balance and reduced nicotinamide adenine dinucleotide phosphate generation. The data in this paper in conjunction with published information support the notion of different molecular forms of a protein functioning in different metabolic pathways which have common enzymic steps.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=366285Documentos Relacionados
- Metabolic Changes Associated with Adaptation of Plant Cells to Water Stress 1
- The Effect of Adenine Nucleotides on Purified Phosphoenolpyruvate Carboxylase from the CAM Plant Crassula argentea1
- Metabolic Analysis of Escherichia coli in the Presence and Absence of the Carboxylating Enzymes Phosphoenolpyruvate Carboxylase and Pyruvate Carboxylase
- Light Modulation of Maize Leaf Phosphoenolpyruvate Carboxylase 1
- Malate Inhibition of Phosphoenolpyruvate Carboxylase from Crassula1