In the second article of the Rare Sugars Series, rare sugars were shown to be producible using various enzymes (e.g., aldose isomerase, ketose 3-epimerase, polyol dehydrogenase), and the Izumoring was introduced as a key element in a strategy for comprehensive production of rare six-carbon hexoses by combining their enzymatic reactions. In this article, we describe the use of ketose 3-epimerase for producing the rare sugar D-allulose (=D-psicose) from naturally abundant D-fructose, and the use of L-rhamnose isomerase for producing the rare sugar D-allose from the thus-produced D-allulose. Currently, there are no “rare sugar producing enzymes” that catalyze the production of rare sugars, that is, sugars found in low abundance in a natural environment. However, enzymes capable of catalyzing the conversion of non-rare sugars to rare sugars exist in nature. We characterized some microbial enzymes that we successfully used to produce rare sugars, and the results are reported below. ...and more
This article focuses on the crystal structures of monosaccharides and rare sugars and explores how the molecules interact with each other (i.e., intermolecular interaction) and how this interaction affects the morphology and properties of the crystals. Examining these points reveals the characteristics of a substance. There are molecules that have very similar molecular structures but very different crystal structures; for example, D-glucose and D-allose, or D-fructose and D-allulose. I am attempting to clarify these structural differences and to elucidate the underlying mechanisms of hydrogen bond formation and intermolecular interactions. I am also investigating the potential for novel applications of rare sugar crystals, and here I present an approach on how to control the crystal structure to obtain a specific physical property. In addition, this article provides a new perspective on the longstanding mystery of whether the crystal structure of monosaccharides can be controlled. I hope that through this article, readers will gain a concrete understanding of research progress in the application of rare sugar crystals and will be inspired to learn how the knowledge of crystal structures can contribute to materials science, medicine, agriculture, and other fields. ...and more
In this second article of the series, we describe the development history of the strategy map for the systematic production of all hexoses (Izumoring), the significance of the production strategy map, problems that have become apparent in Izumoring-based rare sugar production, and a new strategy map for rare sugar production (Izumoring Ⅱ) developed to solve these problems. We also introduce a simplified version of the Fischer projection formula for monosaccharides (Izumofleet formula), which is used in the new strategy map for rare sugar production. ...and more
This article series provides an introduction to rare sugars. The authors of this series are experts from industrial, academic, and governmental sectors, mainly members of the International Institute of Rare Sugar Research and Education, Kagawa University. Beginning with an explanation of what rare sugars are, we introduce the basic properties of rare sugars. We then provide an easy-to-understand overview of the current status of the applications of rare sugars in a variety of fields.
This is the first article of the series; the topics are "What is a rare sugar?" and "History of rare sugars". ...and more
