Inter-species variation of malate sensitivity of PEP carboxylase in CAM plants and the mechanism of the regulation

以13种CAM植物为研究对象，研究了磷酸烯醇丙酮酸羧化酶（PEPC）的最适pH值和PEPC对苹果酸盐敏感性的种间差异；PEPC的最适pH值在种间存在显著差异。其中香草香料的PEPC有两个最优ph值。结果表明，紫丁香中PEPC同工酶存在。PEPC对苹果酸盐的敏感性也存在物种差异。结果表明，丁香属植物对苹果酸盐的敏感性呈现明显的昼夜变化。前叶景天被归类为anas类型，不显示昼夜变化。蝴蝶兰、普通机会花、石斛、山茱萸、金银花、金银花、麝香芦荟、非洲蕨属属，属上述类型的中间品种。以三种CAM植物——小茴香（anansucomosus）、凤尾花（kalanche daigremontiana）和凤尾花（k.p ynata）对苹果酸盐具有不同的PEPC敏感性，研究了PEPC在细胞中的定位及其等电聚焦特性。三种CAM植物的叶肉细胞中PEPC的位置不同。在石竹中，PEPC主要存在于细胞质和生物膜中。在鸡毛草中，PEPC主要分布在细胞质和生物膜表面。大部分的PEPC（80%以上）存在于生物膜中。因此，CAM物种对苹果酸盐敏感性的差异可能与PEPC的细胞间位置有关。等电点分别为5.1 ~ 5.2和5.8 ~ 5.9。

Using 13 CAM species, optimum pH of phosphoenolpyruvate carboxylase(PEPC)and inter-species variation of malate sensitivities of PEPC were studied ; Optimum pH of PEPC showed significant intre-species difference among species. Especially Vanilla fragrant showed two optimum pHs of PEPC.This suggested the isozyme of PEPC in V.fragrant. Malate sensitivity of PEPC also showed difference in species. V.fragrant was grouped into the type of pinnata, which showed clear day/night change of the malate sensitivity. Sedum praealtum was classified to the type of ananas, which did not show the day/night change. Phalaenopsis, Opuntia vulgaris, Dendrobium ekapol, Hoya carnosa, Crassula argentea, Aloe thraskii, Porturacaria afra were grouped into the type of daigremontiana, which showed intermediate of above types.Using three CAM plants, Anansu comosus, Kalanchoe daigremontiana, and K.pinnata, which showed different malate sensitivity of PEPC,located of PEPC in the cell and characteristics of isoelectric focusing were studied. The location of PEPC in the mesophyll cell was in different among three CAM plants. In K.pinnata, PEPC located mainly in cytosol and biomembrane. In A.comosus, PEPC distributed in the cytosol and on the surface of biomembrane. Most of PEPC of K.daigremontiana, more than 80%, existed in the biomembrane. Consequently, it was suggested that the difference of malate sensitivity in CAM species related to the inter-cellular location of PEPC.Isoelectric point of A.comosus, and K.pinnata and K.daigremonteana, was observed at 5.1 to 5.2, and 5.8 to 5.9, respectively.