Trends in Glycoscience and Glycotechnology
Online ISSN : 1883-2113
Print ISSN : 0915-7352
ISSN-L : 0915-7352
Structure and Function of Branching Enzymes in Eukaryotes
Ryuichiro Suzuki Eiji Suzuki
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2020 Volume 32 Issue 185 Pages E21-E30


Brancihing enzymes (BEs) catalyze the transglycosylation reactions to form a new branching point consisting of an α-1,6-glucosidic linkage by cleaving an α-1,4-glucosidic linkage of an α-glucan chain. BEs are ubiquitous throughout the prokaryotes but are only found in limited taxa in the eukaryotes. Prokaryotic and eukaryotic BEs are classified into distinct families based on similarities in their primary structures. Land plants have multiple BE isoforms, whose function in vivo has been identified using mutants. Recent studies have revealed that plant BEs form protein–protein complexes with related enzymes involved in α-glucan metabolism in vivo. Although their biological significance is unclear, it is proposed that they are essential for efficient amylopectin biosynthesis. Crystal structures of BEs from eukaryotes (rice and human) are now available. These two structures have the same domain organization, containing a catalytic domain common to all members of glycoside hydrolase family 13. Recently, the authors have reported the structures of BE from a cyanobacterium (a photosynthetic prokaryote) in complex with maltooligosaccharides at the active site. On the other hand, little is known about the structure–function relationship of eukaryotic BEs. This review describes recent progress in research on the structure and function of eukaryotic BEs.

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© 2020 FCCA (Forum: Carbohydrates Coming of Age)
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