2023-05-10 米国国立再生可能エネルギー研究所(NREL)
◆ガラクタンシンターゼ1(GalS1)という酵素は、糖のガラクトースをガラクタンという重合体に変化させるが、これはペクチンの重要な構成要素である。GalS1のような酵素を過剰発現させたり、改変したりすることで、細胞壁の特性に影響を与え、ペクチンやその他の主要なポリマーの化学組成を変えることができる。
◆この研究は、持続可能なバイオ製品の製造や、より効率的なバイオ燃料の開発に利用される可能性があります。
<関連情報>
- https://www.nrel.gov/news/program/2023/a-pectin-synthesizing-enzyme-may-help-trees-weather-storms-could-be-key-to-more-sustainable-bioproducts.html
- https://www.nature.com/articles/s41477-023-01358-4
植物のモジュラー型β-1,4-ガラクタン合成酵素の構造・生化学的知見 Structural and biochemical insight into a modular β-1,4-galactan synthase in plants
Pradeep Kumar Prabhakar,Jose Henrique Pereira,Rahil Taujale,Wanchen Shao,Vivek S. Bharadwaj,Digantkumar Chapla,Jeong-Yeh Yang,Yannick J. Bomble,Kelley W. Moremen,Natarajan Kannan,Michal Hammel,Paul D. Adams,Henrik V. Scheller & Breeanna R. Urbanowicz
Nature Plants Published:27 February 2023
DOI:https://doi.org/10.1038/s41477-023-01358-4
Abstract
Rhamnogalacturonan I (RGI) is a structurally complex pectic polysaccharide with a backbone of alternating rhamnose and galacturonic acid residues substituted with arabinan and galactan side chains. Galactan synthase 1 (GalS1) transfers galactose and arabinose to either extend or cap the β-1,4-galactan side chains of RGI, respectively. Here we report the structure of GalS1 from Populus trichocarpa, showing a modular protein consisting of an N-terminal domain that represents the founding member of a new family of carbohydrate-binding module, CBM95, and a C-terminal glycosyltransferase family 92 (GT92) catalytic domain that adopts a GT-A fold. GalS1 exists as a dimer in vitro, with stem domains interacting across the chains in a ‘handshake’ orientation that is essential for maintaining stability and activity. In addition to understanding the enzymatic mechanism of GalS1, we gained insight into the donor and acceptor substrate binding sites using deep evolutionary analysis, molecular simulations and biochemical studies. Combining all the results, a mechanism for GalS1 catalysis and a new model for pectic galactan side-chain addition are proposed.
