Fractionation of Stable Carbon Isotopes by Phosphoenolpyruvate Carboxylase from C4 Plants 1
AUTOR(ES)
Reibach, Paul H.
RESUMO
The active species of “CO2” and the amount of fractionation of stable carbon isotopes have been determined for a partially purified preparation of phosphoenolpyruvate (PEP) carboxylase (EC 4.1.1.31) from corn (Zea mays) leaves. The rates of the enzyme reactions, using substrate amounts of HCO3−, CO2 or CO2 plus carbonic anhydrase, show that HCO3− is the active species of “CO2” utilized by PEP carboxylase. The Km values for CO2 and HCO3− are 1.25 mm and 0.11 mm, respectively, which further suggest the preferential utilization of HCO3− by PEP carboxylase. The amount of fractionation of stable carbon isotopes by PEP carboxylase from an infinite pool of H12CO3− and H13CO3− was −2.03‰. This enzyme fractionation (δ), together with the fractionation associated with absorption of CO2 into plant cells and the equilibrium fractionation associated with atmospheric CO2 and dissolved HCO3− are discussed in relation to the fractionation of stable carbon isotopes of atmospheric CO2 during photosynthesis in C4 plants.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=542449Documentos Relacionados
- Enzymatic Fractionation of Carbon Isotopes by Phosphoenolpyruvate Carboxylase from C4 Plants 1
- Comparative Studies of Phosphoenolpyruvate Carboxylase from C3 and C4 Plants 1
- Enzymic Fractionation of the Stable Carbon Isotopes of Carbon Dioxide by Ribulose-1,5-bisphosphate Carboxylase 1
- Fractionation of the Stable Isotopes of Inorganic Carbon by Seagrasses 1
- Carbon Isotopic Fractionation Does Not Occur during Dark Respiration in C3 and C4 Plants.
