Abstract

The first part of this work consists in the identification of a prokaryotic-type bifunctional enzyme (aspartate aminotransferase, PT-AAT) in photosynthetic cells of Sorghum–sudangrass hybrid seeds Sorghum × drummondii (Nees ex Steud.) Millsp. and Chase. The results obtained show that the enzyme is constituted by a subunit of 45 kDa immunologically similar to the enzymes of C₃ plants and gymnosperms. This result suggests a high degree of conservation of the PT-AAT in higher plants. To investigate whether the expression of AAT is associated with the differentiation of leaves, we analyzed the chlorophyll levels and AAT, glutamine synthetase (GS), glutamate synthase (GOGAT), isocitrate dehydrogenase (IDH), Rubisco and nitrate reductase (NR) contents in serial sections of the leaves. The chlorophyll content was high in the top sections; and then decreased toward basal sections in a continuous gradient. The Rubisco and NR contents matched the pattern of chlorophyll in the leaves with high levels in the aged section and very low levels in the basal sections. In contrast to chlorophyll, Rubisco and NR contents, GS₂ and Fd-GOGAT polypeptides markedly increased from the top to the basal sections of leaves. However the patterns of AAT and IDH polypeptides did not change in different sections. In the second part of this work, to determine the relative localization of AAT, mesophyll cells (MCs) and bundle-sheath cells (BSCs) of sorghum leaves were separated by cellulase and macerase digestion. PT-AAT protein was most abundant in MC fraction than BSC fraction.

中文翻译：

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高粱叶中的原核型天冬氨酸氨基转移酶：定位，分布和潜在的作用。

摘要

这项工作的第一部分在于鉴定高粱-苏丹草杂交种子高粱×德兰蒙地（Nees ex Steud。）Millsp的光合细胞中的原核生物型双功能酶（天冬氨酸氨基转移酶，PT-AAT）。和大通。获得的结果表明，该酶由45 kDa的亚基组成，在免疫学上类似于C ₃的酶。植物和裸子植物。该结果表明高等植物中PT-AAT的高度保守性。为了研究AAT的表达是否与叶片分化有关，我们分析了AAT的叶绿素水平和AAT，谷氨酰胺合成酶（GS），谷氨酸合成酶（GOGAT），异柠檬酸脱氢酶（IDH），Rubisco和硝酸还原酶（NR）的含量。叶子的连续部分。顶部的叶绿素含量高；然后以连续的梯度向基底部分减小。Rubisco和NR含量与叶片中叶绿素的模式相匹配，其中老龄部分的叶绿素含量高，而基础部分的叶绿素含量很低。与叶绿素，Rubisco和NR含量相反，GS ₂Fd-GOGAT多肽和Fd-GOGAT多肽从叶的顶部到底部显着增加。但是，AAT和IDH多肽的模式在不同部分没有变化。在这项工作的第二部分中，为了确定AAT的相对定位，通过纤维素酶和浸渍酶消化法分离了高粱叶的叶肉细胞（MCs）和束鞘细胞（BSCs）。PT-AAT蛋白在MC组分中比BSC组分最丰富。