Charles S A, Halliwell B
Biochem J. 1981 Nov 15;200(2):357-63. doi: 10.1042/bj2000357.
The fructose bisphosphatase (EC 3.1.3.11) activity of type A chloroplasts isolated from young (9-day-old) pea (Pisum sativum var. Progress no. 9) plants, assayed at physiological pH, substrate and Mg2+ concentrations, increased rapidly on illumination. The enzyme activity detected was more than sufficient to account for observed rates of Co2 fixation both during the induction period and during steady-state CO2 fixation, whether or not dihydroxyacetone phosphate had been added to the preparation. Omission of catalase from the suspension medium had no effect. On switching off the light, CO2 fixation by the chloroplasts ceased at once, yet fructose bisphosphatase activity decreased much more slowly. Changes in enzyme activity were much less marked if assays were conducted at 3 mM substrate and 10 mM-Mg2+. Chloroplasts from older (13--20-day-old) peas only fixed CO2 rapidly if catalase was present in the assay medium. The fructose bisphosphatase activity detected under physiological assay conditions was again more than sufficient to account for observed rates of Co2 fixation. In the presence of added dihydroxyacetone phosphate, however, the rate of Co2 fixation appeared to be determined by the rate of light activation of fructose bisphosphatase. In general, the rates of Co2 fixation and enzyme activation, and the final enzyme activity achieved, decreased markedly with increasing age of the plants. The role of light activation of fructose bisphosphatase as a means of controlling the rate of CO2 fixation in pea chloroplasts is discussed.
从9日龄的豌豆（豌豆品种Progress no. 9）幼苗中分离出的A型叶绿体，在生理pH值、底物和Mg2+浓度条件下测定的果糖二磷酸酶（EC 3.1.3.11）活性，在光照下迅速增加。无论制备物中是否添加了磷酸二羟丙酮，在诱导期和稳态二氧化碳固定期间，检测到的酶活性都足以解释观察到的二氧化碳固定速率。悬浮培养基中省略过氧化氢酶没有影响。关闭光源后，叶绿体的二氧化碳固定立即停止，但果糖二磷酸酶活性下降得要慢得多。如果在3 mM底物和10 mM - Mg2+条件下进行测定，酶活性的变化则不太明显。只有在测定培养基中存在过氧化氢酶时，来自13 - 20日龄老豌豆的叶绿体才能快速固定二氧化碳。在生理测定条件下检测到的果糖二磷酸酶活性同样足以解释观察到的二氧化碳固定速率。然而，在添加了磷酸二羟丙酮的情况下，二氧化碳固定速率似乎由果糖二磷酸酶的光激活速率决定。一般来说，随着植株年龄的增加，二氧化碳固定速率、酶激活速率以及最终达到的酶活性都显著下降。本文讨论了果糖二磷酸酶的光激活在控制豌豆叶绿体二氧化碳固定速率中的作用。
