Department of Pure and Applied Sciences, College of Arts and Sciences, University of Tokyo, Tokyo 153.
Plant Physiol. 1985 Nov;79(3):829-32. doi: 10.1104/pp.79.3.829.
Light-induced swelling of guard cell protoplasts (GCP) from Vicia faba was accompanied by increases in content of K(+) and malate. DCMU inhibited the increase of K(+) and malate, and consequently swelling.Effect of light on the activity of selected enzymes that take part in malate formation was studied. When isolated GCP were illuminated, NADP-malate dehydrogenase (NADP-MDH) was activated, and the activity reached a maximum within 5 minutes. The enzyme activity underwent 5- to 6-fold increase in the light. Upon turning off the light, the enzyme was inactivated in 5 minutes NAD-MDH and phosphoenolpyruvate carboxylase (PEPC) were not influenced by light. The rapid light activation of NADP-MDH was inhibited by DCMU, suggesting that the enzyme was activated by reductants from the linear electron transport in chloroplasts. An enzyme localization study by differential centrifugation indicates that NADP-MDH is located in the chloroplasts, NAD-MDH in the cytosol and mitochondria, and PEPC in the cytosol. After light activation, the activity of NADP-MDH in guard cells was 10 times that in mesophyll cells on a chlorophyll basis. The physiological significance of light-dependent activation of NADP-MDH in guard cells is discussed in relation to stomatal movement.
蚕豆保卫细胞原生质体（GCP）的光诱导肿胀伴随着 K(+)和苹果酸含量的增加。DCMU 抑制 K(+)和苹果酸的增加，从而抑制肿胀。研究了光对参与苹果酸形成的选定酶活性的影响。当分离的 GCP 被照射时，NADP-苹果酸脱氢酶（NADP-MDH）被激活，并且在 5 分钟内达到最大活性。该酶的活性在光下增加了 5-6 倍。当关闭光时，NAD-MDH 和磷酸烯醇丙酮酸羧化酶（PEPC）在 5 分钟内失活。DCMU 抑制 NADP-MDH 的快速光激活，表明该酶被叶绿体线性电子传递中的还原剂激活。差速离心的酶定位研究表明，NADP-MDH 位于叶绿体中，NAD-MDH 位于细胞质和线粒体中，PEPC 位于细胞质中。光激活后，以叶绿素为基础，保卫细胞中 NADP-MDH 的活性是叶肉细胞的 10 倍。讨论了保卫细胞中 NADP-MDH 的光依赖性激活与气孔运动的关系及其生理意义。
