INVITRO AND INSITU PROPERTIES OF CELL-WALL PECTINMETHYLESTERASES FROM MUNG BEAN HYPOCOTYLS
INVITRO AND INSITU PROPERTIES OF CELL-WALL PECTINMETHYLESTERASES FROM MUNG BEAN HYPOCOTYLS
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DOI：
10.1093/jxb/43.1.41
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发表时间：
1992-01-01
影响因子：
6.9
通讯作者：
MUTAFTSCHIEV, S
中科院分区：
文献类型：
--
作者：
GOLDBERG, R;PIERRON, M;MUTAFTSCHIEV, S
果胶甲酯酶（EC 3.1.1.11）已从绿豆下胚轴的幼组织和成熟组织中溶解。无论组织的塑性潜力，大部分的果胶甲酯酶活性位于细胞壁。在CM Sepharose上层析后得到几个活性级分。在分析ultracentrance ge的平衡沉降表明分离的异构体的MW接近75000，而SDS-PAGE电泳给出了MW约32000，这表明二聚体结构的可能性。绿豆果胶甲酯酶（PME）与大豆抗血清有交叉反应。对硝基苯乙酸酯和柑橘果胶的实验表明，PME和酯酶活性可能对应于不同的异构体。还注意到，当酶与细胞壁结合时，阳离子诱导的刺激更强。高离子灵敏度表明。离子环境原位调节果胶甲酯酶活性主要是通过修饰果胶分子，这增强了酶对其底物的亲和力。这些数据表明，细胞壁的钙含量的重要性，并可能解释甲基化果胶沿着绿豆下胚轴的减少，反过来，可塑性的损失。
Pectinmethylesterases (EC 3.1.1.11) have been solubilized from young and mature tissues of mung bean hypocotyls. Whatever the plastic potential of the tissues, most of the pectinmethylesterase activity was located in the cell walls. Several active fractions were obtained after chromatography on CM Sepharose. Equilibrium sedimentation in an analytical ultracentrifuge indicated the MW of the isolated isoforms to be close to 75000 whereas SDS-PAGE electrophoresis gave a MW around 32000, suggesting the possibility of dimeric structures. Mung bean pectinmethylesterase (PME) showed cross reactivity with soybean antiserum. Experiments carried out with p-nitrophenylacetate and Citrus pectin revealed that PME and esterase activities might correspond to different isoforms. It was also noted that the stimulation induced by cations was stronger when the enzymes were bound to the cell walls. The high ionic sensitivity suggested that. in situ, the ionic environment regulates pectinmethylesterase activity principally by modifying the pectin molecules, which enhances the affinity of the enzymes for their substrate. These data indicate the importance of the calcium content of the cell walls and might explain the decrease in methylated pectins along the mung bean hypocotyl and, in turn, the loss of plasticity.