Carotenoid Cyclase Enzymes from Arabidopsis thaliana: Structure, Function, and Interactions

小行星9631257 番茄红素的环化反应是类胡萝卜素生物合成途径中的一个关键分支。 在高等植物类胡萝卜素中通常发现两种类型的环状端基：（和（环化酶由拟南芥中的同源基因编码，并且这两种酶都使用线性、对称的番茄红素作为底物。 然而，环化酶仅添加一个环，而环化酶在分子的两端引入一个环。 本研究的目的是检测和比较A. thaliana，以确定这两种酶内的功能区域和氨基酸残基，并确定环化酶-环化酶相互作用是否在酶功能中起作用。 具有环状端基的类胡萝卜素是所有植物、藻类和蓝藻的光合膜的基本组分。 这些脂溶性化合物保护免受光氧化，收获光合作用的光，并消散天线色素吸收的多余光能。 类胡萝卜素色素在光合膜中的积累与光合机构的生物合成和组装密切相关。 用于协调这些过程的调节机制是模糊的。 经典的生物化学方法在类胡萝卜素途径的膜相关酶的研究中价值有限，因此所采取的方法主要是遗传方法。 这项研究的结果将提供有价值的信息，类胡萝卜素生物合成的基本植物途径的操作和控制，并可以提供其他代谢途径，涉及膜相关的多酶复合物的功能和调节的见解。

9631257 Cunningham The cyclization of lycopene is a key branch point in the pathway carotenoid biosynthesis. Two types of cyclic end groups are commonly found in higher plant carotenoids: the ( and ( cyclase enzymes are encoded by homologous genes in Arabidopsis thaliana, and both enzymes us the linear, symmetrical lycopene as a substrate. However, the ( cyclase adds only one ring while the ( cyclase introduces a ring at both ends of the molecule. The objectives of this research are to examine and compare substrate utilization and product formation by the ( and ( cyclases of A. thaliana, to identify functional regions and amino acid residues within these two enzymes, and to ascertain whether cyclase-cyclase interactions play a role in enzyme function. Carotenoids with cyclic end groups are essential components of the photosynthetic membranes in all plants, algae and cyanobacteria. These lipid-soluble compounds protect against photooxidation, harvest light for photosynthesis, and dissipate excess light energy absorbed by the antenna pigments. The accumulation of carotenoid pigments in the photosynthetic membranes is closely coordinated with the biosynthesis and assembly of the photosynthetic apparatus. The regulatory mechanisms that serve to coordinated these processes are obscure. The classical biochemical approaches have been of limited value in the study of the membrane-associated enzymes of the carotenoid pathway, therefore the approach to be taken is largely a genetic one. The results of this research will provide valuable information on the operation and control of the essential plant pathway of carotenoid biosynthesis, and can provide insights on the functioning and regulation of other metabolic pathways that involve membrane-associated multienzyme complexes.