Centre de Physiologie Végétale, URA 241 CNRS, Université Paul Sabatier, 31062, Toulouse Cédex, France.
Photosynth Res. 1989 Nov;22(2):147-55. doi: 10.1007/BF00035445.
The activity of corn phosphoglycolate phosphatase (EC 3.1.3.18), a bundle sheath chloroplastic enzyme, is modulated, in vitro, both by NADP(H) and adenylate energy charge. The Vmax of the enzyme is increased by NADP (25%) and NADPH (16%) whatever the pH used, 7.0 or 7.9 respective pH of the stroma in the dark and in the light. At both pH, the adenylate energy charge alone has a positive effect with two peaks of activation, characteristics for this enzyme, at 0.2 and a maximum at 0.8 accentuated under nonsaturating concentration of phosphoglycolate. At low energy charge, NADP(H) increased the activation with an additive effect most particularly observed at pH 7.9 under saturating phosphoglycolate concentration; at high energy charge, NADP(H) had a positive or negative effect on the activation, depending on the pH value and the concentrations of substrate and NADP(H).The ferredoxin-thioredoxin system does not regulate the activity since i) DTT addition do not have any effect, ii) the light-reconstituted system containing ferredoxin, ferredoxin-thioredoxin reductase, thioredoxins and thylakoids is not effective either. However, light-dark experiments indicate that phosphophycolate phosphatase can be subjected to a fine tuning of its activity.All these data suggest that light cannot induce a modification of the protein but could exert a tight control of its activity by the intermediate of Mg(2+) and substrate concentrations and the levels of metabolites such as NADP(H), ATP, ADP, AMP. So, the regulation of the activity shown, in vitro, by energy charge and NADP(H) might be of physiological significance.
玉米磷酸烯醇式丙酮酸磷酸酶（EC3.1.3.18）的活性是一种束鞘质体叶绿体酶，它在体外受到 NADP（H）和腺苷酸能量电荷的调节。无论使用的 pH 值是 7.0 还是 7.9（分别为暗中和光下基质的 pH 值），NADP（25%）和 NADPH（16%）都能增加酶的 Vmax。在这两种 pH 值下，仅腺苷酸能量电荷就具有正效应，有两个激活峰，这是该酶的特征，在 0.2 和最大 0.8 处，在非饱和浓度的磷酸烯醇式丙酮酸下增强。在低能量电荷下，NADP（H）通过添加效应增加激活，在饱和磷酸烯醇式丙酮酸浓度下，在 pH7.9 下尤其明显；在高能量电荷下，NADP（H）对激活有正或负的影响，这取决于 pH 值、底物和 NADP（H）的浓度。铁氧还蛋白-硫氧还蛋白系统不调节活性，因为 i）添加 DTT 没有任何影响，ii）含有铁氧还蛋白、铁氧还蛋白-硫氧还蛋白还原酶、硫氧还蛋白和类囊体的光再组成系统也没有效果。然而，光-暗实验表明，磷酸烯醇式丙酮酸磷酸酶的活性可以进行精细调节。所有这些数据表明，光不能诱导蛋白质的修饰，但可以通过中间物 Mg2+和底物浓度以及代谢物如 NADP（H）、ATP、ADP、AMP 的水平，对其活性进行紧密控制。因此，体外显示的由能量电荷和 NADP（H）调节的活性可能具有生理意义。
