Hatch M D, Burnell J N
Division of Plant Industry, CSIRO, GPO Box 1600, Canberra ACT 2601, Australia.
Plant Physiol. 1990 Jun;93(2):825-8. doi: 10.1104/pp.93.2.825.
In C(4) plants carbonic anhydrase catalyzes the critical first step of C(4) photosynthesis, the hydration of CO(2) to bicarbonate. The maximum activity of this enzyme in C(4) leaf extracts, measured by H(+) production with saturating CO(2) and extrapolated to 25 degrees C, was found to be 3,000 to 10,000 times the maximum photosynthesis rate for these leaves. Similar activities were found in C(3) leaf extracts. However, the calculated effective activity of this enzyme at in vivo CO(2) concentrations was apparently just sufficient to prevent the rate of conversion of CO(2) to HCO(3) (-) from limiting C(4) photosynthesis. This conclusion was supported by the mass spectrometric determination of leaf carbonic anhydrase activities.
在C4植物中,碳酸酐酶催化C4光合作用的关键第一步,即CO2水合形成碳酸氢盐。通过在饱和CO2条件下测定H+产生量并外推至25℃,发现该酶在C4叶片提取物中的最大活性是这些叶片最大光合速率的3000至10000倍。在C3叶片提取物中也发现了类似的活性。然而,在体内CO2浓度下计算得出的该酶有效活性显然仅足以防止CO2转化为HCO3(-)的速率限制C4光合作用。这一结论得到了叶片碳酸酐酶活性的质谱测定结果的支持。