Form of Inorganic Carbon Involved as a Product and as an Inhibitor of C4 Acid Decarboxylases Operating in C4 Photosynthesis
Open Access
- 1 December 1987
- journal article
- research article
- Published by Oxford University Press (OUP) in Plant Physiology
- Vol. 85 (4) , 952-957
- https://doi.org/10.1104/pp.85.4.952
Abstract
These studies demonstrated that CO2 rather than HCO3− is the inorganic carbon metabolite produced by the C4 acid decarboxylases involved in C4 photosynthesis (chloroplast located NADP malic enzyme, mitochondrial NAD malic enzyme, and cytosolic phosphoenolpyruvate [PEP] carboxykinase). The effect of varying CO2 or HCO3− as a substrate for the carboxylation reaction catalyzed by these enzymes or as inhibitors of the decarboxylation reaction was also determined. The KmCO2 was 1.1 millimolar for NADP malic enzyme and 2.5 millimolar for PEP carboxykinase. For these two enzymes the velocity in the carboxylating direction was substantially less than for the decarboxylating direction even with CO2 concentrations at the upper end of the range of expected cellular levels. Activity of NAD malic enzyme in the carboxylating direction was undetectable. The decarboxylation reaction of all three enzymes was inhibited by added HCO3−. For NADP malic enzyme CO2 was shown to be the inhibitory species but PEP carboxykinase and NAD malic enzyme were apparently inhibited about equally by CO2 and HCO3−.Keywords
This publication has 20 references indexed in Scilit:
- Mechanism of C4 PhotosynthesisPlant Physiology, 1987
- Determination of NAD Malic Enzyme in Leaves of C4 PlantsPlant Physiology, 1982
- NADP-malic enzyme from maize leaf: Purification and propertiesArchives of Biochemistry and Biophysics, 1979
- Regulation of mitochondrial NAD-malic enzyme involved in C4 pathway photosynthesisArchives of Biochemistry and Biophysics, 1977
- Association of NADP- and NAD-linked malic enzyme activities in Zea mays: Relation to C4 pathway photosynthesisArchives of Biochemistry and Biophysics, 1977
- Properties of leaf NAD malic enzyme from plants with C4 pathway photosynthesisArchives of Biochemistry and Biophysics, 1974
- Alkalization of the chloroplast stroma caused by light-dependent proton flux into the thylakoid spaceBiochimica et Biophysica Acta (BBA) - Bioenergetics, 1973
- The C4-pathway of photosynthesis. Evidence for an intermediate pool of carbon dioxide and the identity of the donor C4-dicarboxylic acidBiochemical Journal, 1971
- Isolation and properties of a ‘malic’ enzyme from cauliflower bud mitochondriaBiochemical Journal, 1971
- The mechanisms of reductive carboxylation reactions. Carbon dioxide or bicarbonate as substrate of nicotinamide-adenine dinucleotide phosphate-linked isocitrate dehydrogenase and ‘malic’ enzymeBiochemical Journal, 1968