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Simultaneous determination of Rubisco carboxylase and oxygenase kinetic parameters in Triticum aestivum and Zea mays using membrane inlet mass spectrometry
Author(s) -
COUSINS A. B.,
GHANNOUM O.,
VON CAEMMERER S.,
BADGER M. R.
Publication year - 2010
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1111/j.1365-3040.2009.02095.x
Subject(s) - enzyme kinetics , rubisco , chemistry , kinetics , carboxylation , mass spectrometry , analytical chemistry (journal) , photosynthesis , chromatography , enzyme , biochemistry , active site , catalysis , physics , quantum mechanics
The lack of complete Rubisco kinetic data for numerous species is partly because of the time consuming nature of the multiple methods needed to assay all of the Rubisco parameters. We have developed a membrane inlet mass spectrometer method that simultaneously determines the rate of Rubisco carboxylation ( v c ) and oxygenation ( v o ), and the CO 2 and O 2 concentrations. Using the collected data, the Michaels‐Menten equations for v c and v o in response to changing CO 2 and O 2 concentrations were simultaneously solved for the CO 2 ( K c ) and O 2 ( K o ) constants, the maximum turnover rates of the enzyme for CO 2 ( k cat CO2 ) and O 2 ( k cat O2 ) and the specificity for CO 2 relative to O 2 ( S c/o ). In the C 4 species Zea mays K c was higher but K o was lower compared with the C 3 species Triticum aestivum. The k cat CO2 was higher and the k cat O2 lower in Z. mays compared with T. aestivum and S c/o was similar in the two species. The V omax / V cmax was lower in Z. mays and thus did not correlate with changes in S c/o . In conclusion, this mass spectrometer system provides a means of simultaneously determining the important Rubisco kinetic parameters, K c , K o , k cat CO2, k cat O2 and S c/o from the same set of assays.