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JXB Advance Access published online on January 27, 2008
Journal of Experimental Botany, doi:10.1093/jxb/erm283
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© The Author [2008]. Published by Oxford University Press [on behalf of the Society for Experimental Biology]. All rights reserved. For Permissions, please e-mail: journals.permissions@oxfordjournals.org

SPECIAL ISSUE REVIEW PAPER

The biochemistry of Rubisco in Flaveria

David S. Kubien1,*, Spencer M. Whitney2, Paige V. Moore1 and Linley K. Jesson1

1Department of Biology, The University of New Brunswick, Box 4400, Fredericton, New Brunswick, E3B 5A3, Canada
2Research School of Biological Sciences, The Australian National University, GPO Box 475, Canberra, ACT 2601, Australia

* To whom correspondence should be addressed. E-mail: kubien{at}unb.ca

C4 plants have been reported to have Rubiscos with higher maximum carboxylation rates (kcatCO2) and Michaelis–Menten constants (Km) for CO2 (Kc) than the enzyme from C3 species, but variation in other kinetic parameters between the two photosynthetic pathways has not been extensively examined. The CO2/O2 specificity (SC/O), kcatCO2, Kc, and the Km for O2 (Ko) and RuBP (Km-RuBP), were measured at 25 °C, in Rubisco purified from 16 species of Flaveria (Asteraceae). Our analysis included two C3 species of Flaveria, four C4 species, and ten C3-C4 or C4-like species, in addition to other C4 (Zea mays and Amaranthus edulis) and C3 (Spinacea oleracea and Chenopodium album) plants. The SC/O of the C4 Flaveria species was about 77 mol mol–1, which was approximately 5% lower than the corresponding value in the C3 species. For Rubisco from the C4 Flaverias kcatCO2 and Kc were 23% and 45% higher, respectively, than for Rubisco from the C3 plants. Interestingly, it was found that the Ko for Rubisco from the C4 species F. bidentis and F. trinervia were similar to the C3 Flaveria Rubiscos (~650 µM) while the Ko for Rubisco in the C4 species F. kochiana, F. australasica, Z. mays, and A. edulis was reduced more than 2-fold. There were no pathway-related differences in Km-RuBP. In the C3-C4 species kcatCO2 and Kc were generally similar to the C3 Rubiscos, but the Ko values were more variable. The typical negative relationships were observed between SC/O and both kcatCO2 and Kc, and a strongly positive relationship was observed between kcatCO2 and Kc. However, the statistical significance of these relationships was influenced by the phylogenetic relatedness of the species.

Key words: C3, C4, Flaveria, kinetics, Michaelis–Menten, phylogeny, Rubisco, specificity

Received 20 September 2007; Revised 16 October 2007 Accepted 22 October 2007


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