Thermal Characteristics of C_4 Photosynthetic Enzymes from Leaves of Three Sugarcane Species Differing in Cold Sensitivity

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Phosphoenolpyruvate carboxylase, NADP-malate dehydrogenase and NADP-malic enzyme in desalted extracts from the leaves of three sugarcane species differing in cold sensitivity were relatively stable at cold temperatures, and their Arrhenius plots appeared as straight lines. Pyruvate, P_i dikinase (PPDK) from the three species was coldinactivated, and its Arrhenius plots exhibited a clear breakpoint around 10.6℃. Analysis of cold lability of PPDK using deuterium oxide and Triton X-100 showed that the interactions between the subunits possibly involve hydrophobic bonds which would lead to cold lability. There were no apparent differences among the three sugarcane species in the thermal properties of the four C_4 photosynthetic enzymes. The results suggest that the differences in cold sensitivity of sugarcane photosynthesis may not relate to the thermal properties of C_4 photosynthetic enzymes perse.
日本植物生理学会の論文