Verification of new mechanistic model of starch branching enzyme

2018 Fiscal Year Final Research Report

• Project/Area Number: 15K18685
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Applied biochemistry
• Research Institution: Akita Prefectural University
• Principal Investigator: Suzuki Ryuichiro 秋田県立大学, 生物資源科学部, 助教 (70632397)
• Project Period (FY): 2015-04-01 – 2019-03-31
• Keywords: 酵素学 / 構造生物学 / 澱粉 / 枝作り酵素

Outline of Final Research Achievements

Branching enzyme (BE) catalyzes formation of branch points of glycogen and starch. Active site cleft (subsite) of BE has never been reported. In this study, crystal structures of BE1 from starch-producing cyanobacteria Cyanothece sp. ATCC 51142 in complex with linear maltooligosaccharides were determined. The crystal structures revealed the location of subsites and the presence of seven surface binding sites (SBSs). Importance of amino acid residues involved in sugar binding at subsites and SBSs in the crystal structures was confirmed by mutational analysis of the residues. In addition, our results suggest that two SBSs in the catalytic domain participate in binding of acceptor substrate. Based on these results, new detailed mechanistic model of BE reaction has been presented.

Free Research Field

酵素学

Academic Significance and Societal Importance of the Research Achievements

澱粉（炭水化物）は人類の主食であり、食品産業・各種工業分野へ応用利用されている。澱粉の構造（分岐パターン）と食味・物性には相関があるが、澱粉の構造を制御する仕組みには未解明の課題が多く残されている。原始的なシアノバクテリアと進化した陸上植物について、澱粉構造の制御メカニズムを解明して比べることは、学術的に重要であり興味深い。応用展開としては、構造を制御した新規澱粉素材の酵素合成技術の確立に向けた第一歩になると期待される。