Interaction of Hydrogen Peroxide with Ribulose-1,5-bisphosphate Carboxylase/Oxygenase from Rice

Sen Li¹, Wei Lu², Guo-Fu Li¹, Yan-Dao Gong¹, Nan-Ming Zhao¹, Rong-Xian Zhang², and Hai-Meng Zhou^1*

¹Department of Biological Science and Biotechnology, Tsinghua University, Beijing 100084, P. R. China; fax: (8610) 6277-2245; E-mail: zhm-dbs@mail.tsinghua.edu.cn

²Department of Agronomy, Nanjing Agricultural University, Nanjing 210095, P. R. China

^* To whom correspondence should be addressed.

Received March 16, 2004; Revision received May 14, 2004

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The properties of rice-derived ribulose-1,5-bisphosphate carboxylase/oxygenase (rubisco) in different concentrations of hydrogen peroxide (H₂O₂) solutions have been studied. The results indicate that at low H₂O₂ concentrations (0.2-10 mM), the properties of rubisco (e.g., carboxylase activities, structure, and susceptibility to heat denaturation) change slightly. However, at higher H₂O₂ concentrations (10-200 mM), rubisco undergoes an unfolding process, including the loss of secondary and tertiary structure, forming extended hydrophobic interface, and leading to cross-links between large subunits. High concentrations of H₂O₂ can also result in an increase in susceptibility of rubisco to heat denaturation. Further pre-treatments with or without reductive reagents to rubisco show that the disulfide bonds in rubisco help to protect the enzyme from damage by H₂O₂ as well as other reactive oxygen species.

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KEY WORDS: rubisco, hydrogen peroxide, unfolding, inactivation

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