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. 1977 Apr;59(4):564–568. doi: 10.1104/pp.59.4.564

Fractionation of Stable Carbon Isotopes by Phosphoenolpyruvate Carboxylase from C4 Plants 1

Paul H Reibach a, C Roy Benedict a
PMCID: PMC542449  PMID: 16659894

Abstract

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.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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