Department of Agronomy, University of Illinois, 61801, Urbana, IL, USA.
Planta. 1984 Jun;161(4):308-13. doi: 10.1007/BF00398720.
The substrate specificity factor, V cKo/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 K c [Km(CO2)] and V c [Vmax (CO2)], which increased by factors of about 10 and 20, respectively, over the temperature range examined. In contrast, K o [Ki (O2)] was unchanged and V o [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.
菠菜（Spinacia oleracea L.）核酮糖 1,5-二磷酸羧化酶/加氧酶的基质特异性因子（V cKo/VoKc）在核酮糖 1,5-二磷酸浓度在 0.63 到 200 μM 之间、pH 值在 7.4 到 8.9 之间以及温度在 5°到 40°之间的条件下进行了测定。在所有核酮糖 1,5-二磷酸浓度下，CO2/O2 的特异性相同，且很大程度上不受 pH 值的影响。随着温度的升高，特异性从 5°时的约 160 降低到 40°时的约 50。温度的主要影响是对 K c [Km(CO2)]和 V c [Vmax (CO2)]，在研究的温度范围内，这两个值分别增加了约 10 倍和 20 倍。相比之下，K o [Ki (O2)]不变，V o [Vmax (O2)]在这些温度下增加了约 5 倍。Γ的 CO2 补偿浓度是从 5°到 40°温度下获得的特异性值计算得到的，并与 Γ的文献值进行了比较。计算值和实测值在定量上是一致的。这里报道的观察结果表明，核酮糖 1,5-二磷酸羧化酶/加氧酶动力学参数的温度响应解释了 C3 植物光合作用/光呼吸比三分之二的温度依赖性，其余三分之一是 CO2 和 O2 的溶解度在温度影响方面的差异所致。
