Biological Trace Element Research

, Volume 121, Issue 3, pp 249–257 | Cite as

Effect of Mg2+ on the Structure and Function of Ribulose-1,5-Bisphosphate Carboxylase/Oxygenase

  • Chen Liang
  • Wu Xiao
  • Huang Hao
  • Liu Xiaoqing
  • Liu Chao
  • Zheng Lei
  • Hong Fashui
Article

Abstract

Mg2+ in various concentrations was added to purified Rubisco in vitro to gain insight into the mechanism of molecular interactions between Mg2+ and Rubisco. The enzyme activity assays showed that the reaction between Rubisco and Mg2+ was two order, which means that the enhancement of Rubisco activity was accelerated by low concentration of Mg2+ and slowed by high concentration of Mg2+. The kinetics constant (Km) and Vmax was 1.91 μM and 1.13 μmol CO2 mg−1 protein∙min−1, respectively, at a low concentration of Mg2+, and 3.45 μM and 0.32 μmol CO2∙mg−1 protein∙min−1, respectively, at a high concentration of Mg2+. By UV absorption and fluorescence spectroscopy assays, the Mg2+ was determined to be directly bound to Rubisco; the binding site of Mg2+ to Rubisco was 0.275, the binding constants (KA) of the binding site were 6.33 × 104 and 5.5 × 104 l·mol−1. Based on the analysis of the circular dichroism (CD) spectra, it was concluded that the binding of Mg2+ did not alter the secondary structure of Rubisco, suggesting that the observed enhancement of Rubisco carboxylase activity was caused by a subtle structural change in the active site through the formation of the complex with Mg2+.

Keywords

Mg2+ Rubisco Enzyme kinetics Spectral characteristic 

Notes

Acknowledgment

This work was supported by the National Natural Science Foundation of China (grant no. 30470150, 20671067) and by the Jiangsu Province Universities Natural Science Foundation (grant no. 06KJB180094).

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Copyright information

© Humana Press Inc. 2007

Authors and Affiliations

  • Chen Liang
    • 1
  • Wu Xiao
    • 1
  • Huang Hao
    • 1
  • Liu Xiaoqing
    • 1
  • Liu Chao
    • 1
  • Zheng Lei
    • 1
  • Hong Fashui
    • 1
  1. 1.College of Life SciencesSuzhou UniversitySuzhouPeople’s Republic of China

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