α-アミラーゼファミリーの概念とそれに基づいたデンプン関連酵素の特異性変換

概要

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A general concept for an enzyme family-the α-amylase family, including most amylases and related enzymes-is proposed and defined based on structural similarities and common catalytic mechanisms. Primary structural analysis, secondary structural predicitions, and three-dimensional structural determinations stimulated this work. However, a series of studies on neopullulanase, which catalyzes both the hydrolysis and transglycosylation at α-1, 4-and α-1, 6-glucosidic linkages by one active center, was the key that opened the door to the concept. On the basis of the proposed α-amylase family concept, the substrate specificity and the ratio of the hydrolysis/transglycosylation activity of neopulluanase were altered. The three-dimensional structure of neopullulanase was predicted by homology modeling. The enzyme-substrate structure was constructed by a docking study and a molecular dynamics calculation. Branching enzyme I and II isoforms from maize endosperm (mBE I and mBE II, respectively) have quite different properties ; to elucidate the domains that determine the differences, chimeric enzymes consisting of part mBE I and part mBE II were constructed. The results indicated that the N-and C-terminus regions of the enzymes are involved in determining substrate preference, catalytic capacity, and chain-length transfer.
社団法人日本生物工学会の論文
2000-04-25