About this Research Topic
Studies of starch metabolism and its biochemical components can be described as having occurred in three stages. One of the most critical discoveries was by Leloir et al. (1961) who demonstrated that α-glucans are synthesized by a “glucan biosynthetic enzyme” (subsequently referred to as starch synthase, SS), which uses a nucleotide-glucose as glucose donor. Later, it was established that ADP-glucose pyrophosphorylase (AGPase), SS, starch branching enzyme (BE) and, more recently, starch debranching enzymes (DBE) are essential enzymes for starch biosynthesis. Many research groups worldwide contributed a variety of results and genetic materials directed towards improving our understanding of the fundamental components of starch biosynthesis in many plant species and organs. By the end of the 1980’s, the basic properties and characteristics of major starch biosynthetic reactions had been revealed, whereas the number of isozymes/subunits of AGPase, SS, BE and DBE, their roles and the genes encoding them, remained largely unresolved.
In the second stage (1990-2010), the introduction of molecular biological approaches into the Plant Sciences accelerated studies on the regulatory molecular mechanisms underpinning starch metabolism, which were enhanced as whole genome information became available. Thus, our understanding of the scope of starch biosynthetic metabolism developed significantly, particularly in relation to the roles of individual isozymes and subunits of starch biosynthetic enzymes in different species and tissues. Based on extensive data, it became possible to draw the skeleton of the complex biochemical processes involved in starch metabolism, and to interpret how and to what extent starch molecular and granular structures, as well as its physicochemical and functional properties, are modified when a specific gene function is altered.
During the third stage, 2011-present, researchers have attempted to characterize and understand the molecular and biochemical mechanisms which regulate starch metabolism in fine detail. To achieve this goal, a combination of in vitro and in vivo studies have proved particularly important to overcome the challenge of functional redundancy, and the interacting contributions among many of the isozymes involved. In the present Research Topic, we will focus on the current status of studies performed world-wide to clarify the mechanisms which regulate starch metabolism using a variety of in vitro and in vivo approaches.
Such an overview is essential for a thorough understanding of the dynamic aspects of distinct regulatory mechanisms between enzymes, and between enzymes and carbohydrates. This focus will provide important insights into the distinct functions of many starch metabolic enzymes and enhance our understanding of the regulation of the complex network of starch metabolic processes.
Keywords: Carbohydrate binding module, Protein-phosphorylation, Starch biosynthesis, Starch branching enzyme, Starch synthase
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