Establishment of enzymatic chemistry (enzymology) of inorganic sulfur compounds and its applications

2021 Fiscal Year Final Research Report

• Project/Area Number: 17K08169
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Environmental agriculture(including landscape science)
• Research Institution: Okayama University
• Principal Investigator: Kanao Tadayoshi 岡山大学, 環境生命科学学域, 准教授 (40379813)
• Project Period (FY): 2017-04-01 – 2022-03-31
• Keywords: 無機硫黄化合物 / 酵素化学 / 硫黄酸化細菌 / 異化的硫黄代謝 / 環境微生物 / 脱硫硫黄 / 独立栄養細菌 / 応用微生物学

Outline of Final Research Achievements

As a target for enzymatic chemistry of inorganic sulfur compounds, we studied tetrathionate hydrolase (<i>Af</i>-Tth) from <i>Acidithiobacillus ferrooxidans</i>, one of the sulfur-oxidizing bacteria. We have already identified a novel gene encoding this enzyme for the first time, and succeeded in obtaining the active form of the recombinant enzyme by acidic refolding treatment, which we originally developed, also in crystallizing it. We are now working to elucidate the unique reaction mechanism of this enzyme by X-ray crystallographic analysis of the obtained crystals together with its substrate, tetrathionate. In this study, we demonstrated that D325 of <i>Af</i>-Tth is an important residue for hydrolyzing tetrathionate molecule.

Free Research Field

応用微生物化学

Academic Significance and Societal Importance of the Research Achievements

硫黄酸化細菌　A. ferrooxidans 由来のテトラチオン酸ハイドロラーゼは、無機硫黄化合物のテトラチオン酸を基質として加水分解し、単体硫黄、チオ硫酸および硫酸を生成するユニークな酵素である。この触媒メカニズムを解明するべく、我々は本酵素のX-線結晶構造解析を行った結果、325番目のアスパラギン酸残基（D325）が基質の加水分解に関わっていることを実証した。現在まで無機硫黄化合物の代謝に関わる酵素は、ほとんどがシステイン残基を介しており、アスパラギン酸残基を触媒とする新たな反応を発見したことは学術的に極めて重要である。また脱硫硫黄の生物的処理への知見を蓄積するため、社会的意義も大きい。