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ID 12355
Eprint ID
12355
FullText URL
Title Alternative
Purification, Characterization and Crystal Structure of Isoamylase from Thermophilic Bacteria Rhodothermus marinus
Author
Tachibana, Akiko
Imada, Katsumi
Kinoshita, Miki
Namba, Keiichi
Tsutsumi, Noriko
Hashida, Miyoko
Sakaguchi, Hiromichi
Abstract
The isoamylase gene from Rhodothermus marinus was cloned into and expressed in Escherichia coli Top 10. As a result of characterization of purified R. marinus isoamylase. the enzyme had an optimum pH of 4.0 and optimum temperature of 70℃. Thermal inactivation studies of the purified R. marinus isoamylase revealed the enzymatic activity to be uninfluenced after one hour incubation at 60℃. These results suggest that R. marinus isoamylase has high thermostability. The crystallization and crystal structure analysis of R. marinus isoamylase was performed. The three-dimensional structure at 1.9Å resolution was determined in complex with the panose. R. marinus isoamylase is composed of three domains N, A and C, and, has a (β/α)8-barrel in domain A. The secondary structural alignments of the R. marinus isoamylase and P. amyloderamosa isoamylase was carried out. They have the four active-site consensus regions characteristic of the α-amylase family. And the essential residue of the α-amylase family (D359, E395, and D467) was conserved in these enzymes. R. marinus isoamylase has shorter loops than P. amyloderamosa isoamylase. And R. marinus isoamylase had no Ca2+ binding site. These results are thought to be factors of thermostability of R. marinus isoamylase.
Abstract Alternative
Rhodothermus marinus 由来イソアミラーゼ遺伝子を組み込んだプラスミド pBX2を使用し,大腸菌 Top10株を形質転換し,16時間の前培養,24時間の本培養後,菌体破砕し,得られた無細胞抽出液を熱処理(80℃,10 min),50オ硫安分画,陰イオン交換カラムクロマトグラフィー(DEAEントヨパール),ハイドロキシアパタイトカラムクロマトグラフィーに供して本酵素の精製を行った.本精製酵素の性質検討を行った結果,本酵素の最適反応温度は70℃,pH4であり,また本酵素は60℃で1時間処理しても活性が低下することが無く,Pseudomonas amyloderamosa 由来イソアミラーゼよりも高い耐熱性を有することが判明した.本酵素の結晶化・X線結晶構造解析を行った結果,本酵素は P. amyloderamosa 由来イソアミラーゼと同様Nドメイン・AドメインCドメインの3つのドメインから構成されており,活性残基(D359,E395,D467)など活性中心付近のアミノ酸残基も P. amyloderamosa 由来イソアミラーゼと同様,高度に保存されていた.本酵素の熱安定性が P. amyloderamosa 由来イソアミラーゼよりも高 い要因として,P. amyloderamosa 由来イソアミラーゼよりもループの長さが全体的に短いことと,カルシウムイオン結合サイトの欠如が挙げられた.今後さらに構造解析を進めることにより,本酵素の熱安定性機構,反応 機構など更なる知見が得られることが期待される.
Keywords
isoamylase
Rhodothermus marinus
crystal structure
thermostability
Published Date
2008-02
Publication Title
岡山大学農学部学術報告
Publication Title Alternative
Scientific Reports of the Faculty of Agriculture Okayama University
Volume
volume97
Issue
issue1
Publisher
岡山大学農学部
Publisher Alternative
Faculty of Agriculture, Okayama University
Start Page
1
End Page
7
ISSN
0474-0254 
NCID
AN00033029
Content Type
Departmental Bulletin Paper
language
日本語
File Version
publisher
Refereed
False
Eprints Journal Name
srfa