Abstract
Amylomaltase is a well-known glucan transferase that can produce large ring cyclodextrins (LR-CDs) or so-called cycloamyloses via cyclization reaction. Amylomaltases have been found in several microorganisms and their optimum temperatures are generally around 60–70 °C for thermostable amylomaltases and 30–45 °C for the enzymes from mesophilic bacteria and plants. The optimum pHs for mesophilic amylomaltases are around pH 6.0–7.0, while the thermostable amylomaltases are generally active at more acidic conditions. Size of LR-CDs depends on the source of amylomaltases and the reaction conditions including pH, temperature, incubation time, and substrate. For example, in the case of amylomaltase from Corynebacterium glutamicum, LR-CD productions at alkaline pH or at a long incubation time favored products with a low degree of polymerization. In this review, we explore the synthesis of LR-CDs by amylomaltases, structural information of amylomaltases, as well as current applications of LR-CDs and amylomaltases.
Highlights
Starch and Cyclodextrin Research Unit, Department of Biochemistry, Faculty of Science, Abstract: Amylomaltase is a well-known glucan transferase that can produce large ring cyclodextrins (LR-CDs) or so-called cycloamyloses via cyclization reaction
LR-CDs can be produced from starch or linear amylose by an enzymatic reaction of 4αGTases, especially the amylomaltases and D-enzymes
Cyclization reactions to produce LR-CDs or CAs were observed in AM, where the smallest LR-CDs reported to be produced is CD16 while the largest is more than CD100 [13,25]
Summary
4-α-Glucanotransferases (4αGTases; EC 2.4.1.25) catalyze a hydrolysis of an α-1,4linkage and a transfer of a (1,4)-α-D-glucan to an acceptor. Members of 4αGTases include amylomaltases from microorganisms and disproportionation enzymes (D-enzymes) from plants and algae, as well as the bacterial cyclodextrin glucanotransferases (CGTases, EC 2.4.1.19). LR-CDs can be produced from starch or linear amylose by an enzymatic reaction of 4αGTases, especially the amylomaltases and D-enzymes. They were first described by Pully and French in 1961 [2]. CGTase can produce LR-CDs from starch as minor side products, while the major products are CD6-8 [3,4]. Nakapong et al., 2022 focused on heterologous expression of 4αGTases including CGTase and amylomaltase for overproduction and beneficial properties for industrial applications [10]. Production of LR-CDs by amylomaltases and the current applications of LR-CDs and amylomaltases are discussed
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