Planta

, Volume 161, Issue 4, pp 308–313

The CO2/O2 specificity of ribulose 1,5-bisphosphate carboxylase/oxygenase

Dependence on ribulosebisphosphate concentration, pH and temperature

Authors

  • Douglas B. Jordan
    • Department of AgronomyUniversity of Illinois
    • Agricultural Research ServiceU.S. Department of Agriculture
  • William L. Ogren
    • Department of AgronomyUniversity of Illinois
    • Agricultural Research ServiceU.S. Department of Agriculture
Article

DOI: 10.1007/BF00398720

Cite this article as:
Jordan, D.B. & Ogren, W.L. Planta (1984) 161: 308. doi:10.1007/BF00398720

Abstract

The substrate specificity factor, VcKo/VoKc, of spinach (Spinacia oleracea L.) ribulose 1,5-bisphosphate carboxylase/oxygenase was determined at ribulosebisphosphate concentrations between 0.63 and 200 μM, at pH values between 7.4 and 8.9, and at temperatures in the range of 5° C to 40° C. The CO2/O2 specificity was the same at all ribulosebisphosphate concentrations and largely independent of pH. With increasing temperature, the specificity decreased from values of about 160 at 5° C to about 50 at 40° C. The primary effects of temperature were on Kc [Km(CO2)] and Vc [Vmax (CO2)], which increased by factors of about 10 and 20, respectively, over the temperature range examined. In contrast, Ko [Ki (O2)] was unchanged and Vo [Vmax (O2)] increased by a factor of 5 over these temperatures. The CO2 compensation concentrations (Γ) were calculated from specificity values obtained at temperatures between 5° C and 40° C, and were compared with literature values of Γ. Quantitative agreement was found for the calculated and measured Γ values. The observations reported here indicate that the temperature response of ribulose 1,5-bisphosphate carboxylase/oxygenase kinetic parameters accounts for two-thirds of the temperature dependence of the photorespiration/photosynthesis ratio in C3 plants, with the remaining one-third the consequence of differential temperature effects on the solubilities of CO2 and O2.

Key words

Carbon dioxide compensation concentrationLeaf photosynthesisPhotorespirationRhodospirillumRibulose 1,5-bisphosphate carboxylase/oxygenaseSpinacia (RuBPCase)

Abbreviations

RuBPC/O(ase)

ribulose 1,5-bisphosphate carboxylase/oxygenase

RuBP

ribulose 1,5-bisphosphate

Γ

CO2 compensation concentration

Copyright information

© Springer-Verlag 1984