Winter H, Huber S C
Fachbereich Biologie/Pflanzenphysiologie, Universität Osnabrück, Germany.
Crit Rev Biochem Mol Biol. 2000;35(4):253-89. doi: 10.1080/10409230008984165.
Sucrose (Suc) plays a central role in plant growth and development. It is a major end product of photosynthesis and functions as a primary transport sugar and in some cases as a direct or indirect regulator of gene expression. Research during the last 2 decades has identified the pathways involved and which enzymes contribute to the control of flux. Availability of metabolites for Suc synthesis and 'demand' for products of sucrose degradation are important factors, but this review specifically focuses on the biosynthetic enzyme sucrose-phosphate synthase (SPS), and the degradative enzymes, sucrose synthase (SuSy), and the invertases. Recent progress has included the cloning of genes encoding these enzymes and the elucidation of posttranslational regulatory mechanisms. Protein phosphorylation is emerging as an important mechanism controlling SPS activity in response to various environmental and endogenous signals. In terms of Suc degradation, invertase-catalyzed hydrolysis generally has been associated with cell expansion, whereas SuSy-catalyzed metabolism has been linked with biosynthetic processes (e.g., cell wall or storage products). Recent results indicate that SuSy may be localized in multiple cellular compartments: (1) as a soluble enzyme in the cytosol (as traditionally assumed); (2) associated with the plasma membrane; and (3) associated with the actin cytoskeleton. Phosphorylation of SuSy has been shown to occur and may be one of the factors controlling localization of the enzyme. The purpose of this review is to summarize some of the recent developments relating to regulation of activity and localization of key enzymes involved in sucrose metabolism in plants.
蔗糖（Suc）在植物生长发育中起着核心作用。它是光合作用的主要终产物，作为主要的运输糖类，在某些情况下还作为基因表达的直接或间接调节因子。过去20年的研究已经确定了相关途径以及哪些酶对通量控制有贡献。蔗糖合成代谢物的可用性和蔗糖降解产物的“需求”是重要因素，但本综述特别关注生物合成酶蔗糖磷酸合酶（SPS）以及降解酶蔗糖合酶（SuSy）和转化酶。最近的进展包括编码这些酶的基因的克隆以及翻译后调控机制的阐明。蛋白质磷酸化正成为响应各种环境和内源性信号控制SPS活性的重要机制。就蔗糖降解而言，转化酶催化的水解通常与细胞扩张有关，而SuSy催化的代谢与生物合成过程（如细胞壁或储存产物）有关。最近的结果表明，SuSy可能定位于多个细胞区室：（1）作为传统上认为的胞质溶胶中的可溶性酶；（2）与质膜相关；（3）与肌动蛋白细胞骨架相关。已证明SuSy会发生磷酸化，这可能是控制该酶定位的因素之一。本综述的目的是总结一些与植物蔗糖代谢中关键酶的活性调节和定位相关的最新进展。
