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GENPLAT: an Automated Platform for Biomass Enzyme Discovery and Cocktail Optimization
Published on: October 24, 2011
Novel type of enzyme multimerization enhances substrate affinity of oat beta-glucosidase
Sang-Yeob Kim1, Yong-Woo Kim, Reiner Hegerl
1Department of Genetic Engineering, College of Natural Science, Kyungpook National University, Daegu 702-701, Republic of Korea.
Abstract:
Oat beta-glucosidase in plastid hydrolyzes avenacosides to C26-desgluco-avenacosides to combat against fungal infections. The enzyme has a unique quaternary protein structure of a three-dimensionally radiated assembly of long fibrillae. We elucidated the fibrillar assembly of oat type 1 beta-glucosidase by means of cryo-electron microscopy, enzyme kinetics and chemical modification. It was assembled by linear stacking of hollow trimeric units and the resulting fibril had a long central tunnel connecting to the outer medium via regularly distributed side fenestrations. The enzyme active sites were located within the central tunnel. This unique multimer assembly increased enzyme affinity to avenacosides, in vivo substrates, and may function to discriminate avenacosides from many other kinds of beta-glucoside in oat. The fibrillar multimer of oat beta-glucosidase is a novel quaternary protein structure for enzyme supramolecular assembly that may have a functional role in the regulation of enzyme affinity.
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