報告書番号

U94055

タイトル（和文）

好熱好酸性水素細菌から精製したヒドロゲナーゼの電極触媒としての適性

タイトル（英文）

CHARACTERIZATION OF HYDROGENASE FROM THERMOACIDOPHILIC AEROBIC HYDROGEN-OXIDIZING BACTERIUM,HYDROGENOBACTER ACIDOPHILUS.

概要 （図表や脚注は「報告書全文」に掲載しております）

当所が分離した好熱好酸性水素細菌Ｈｙｄｒｏｇｅｎｏｂａｃｔｅｒａｃｉｄｏｐｈｉｌｕｓの膜結合型ヒドロゲナーゼの電極触媒として適性を検討した。膜結合型ヒドロゲナーゼの精製を試みたところ，可溶性型ヒドロゲナーゼの場合に比べて非常に高い収率が得られた。精製された膜結合型ヒドロゲナーゼの電極触媒としての特性を検討した結果，この酵素が電子運搬体を介して，燃料電池の水素電極と同じ反応を行えることを確認した。またこの酵素の中心金属の構成は従来の酵素と一致したが，酸素に対する安定性は，既知のヒドロゲナーゼの中では最も安定であると言われるＡ．ｅｕｔｒｏｐｈｕｓの膜結合型ヒドロゲナーゼよりもさらに安定であることが分かった。しかし，酵素活性の高くなる温度領域で触媒作用を失いやすいという短所が見られた。

概要 （英文）

HYDROGENASE IS AN ENZYME OF BACTERIA THAT CATALYZES OXIDATION AND RESUCTION OF MOLECULAR HYDROGEN.THE ENZYME HAS POTEMTIAL AS AN ALTERNATIVE CATALYST FOR EXPENSIVE PLANTINUM. HOWEVER,HYDROGENASE IS VERY SENSITIVE TO OXYGEN AND HIGH TEMPERATURE,SO THAT APPLICATION STUDIES HAVE NOT ADVANCED. A THERMOACIDRHILIC HYDROGEN-OXIDIZINGBACTERIUM,HYDROGENOBACTER ACIDOPHILUS,ISOLATED IN OUR LABORATORY. IT POTENTIAL THAT THE HYSROGENASE OF THE BACTERIUM WAS THERMOSTABLE AND OXYGEN-STABLE IN THE CRUDE EXTRACT.THE PURPOSE OF THIS STUDY WAS PURIFICATION AND CHARACTERIZATION OF MEMBRANE-BOUND HYDROGENASE OF THE BACTERIUM.ALSO,AAPPLICATION OF THE PURIFIED ENZYME AS A CATALYST FOR FUEL CELLS WAS INVESTIGATED. H.ACIDOPHILUS HAD TWO TYPES OF HYDROGENASE: MEMBRANE-BOUND TYPE,AND A SOLUBLE TYPE.THE MEMBRANE-BOUND HYDROGENASE IS MORE OXYGEN-STABLE THAN THE SOLUBLE ONE.THE MEMBRANE-BOUND HYDROGENASE IS ALSOMORE STABLE THAN THE MEMBRANE-BOUND HYDROGENASE OF ALCALIGENUS EUTROPHUS WHICH IS REGARDED AS THE MOST STABLE BACTERIAL HYDROGENASE. A PURIFICATION METHOD WAS DEVELOPED.THE RECOVERY OF HYDROGENASE WAS IMPROVED AND THE YIELD WAS 25 CONVENTIONAL METHODS. THE CHARACTERIZED PURIFIED ENZYME WAS CHARACTERIZED. THE MOLECULAR WEIGHT AND ACTIVE CENTER OF THIS ENZYME IS THE SAME AS CLASS I NIFE HYDROGENASE.THE PURIFIED ENZYME CATALYZED THE REDUCTION OF MOLECULAR HYDROGEN ON A CARBON ELECTRODE WITH METHYLANE BLUE AS AN ELECTRON MEDIATOR.HYDROGEN GENERATION WAS NOT CATALYZED BY THE ENZYME.THE PURIFIED ENZYME SHOWED HIGH ACTIVITY AT HIGH TEMPERATURES(>50 DEGREE)BUT THIS ACTIVITY BELL TO 60% AFTER HALF AN HOUR AT60DEGREE.THESE RESULTS SUGGEST THE ENZYME CAULD BE USED AS AN ELECTRODE CATALYST FOR FUEL CELLS AFTER FURTHER CAULD STABILIZATION AT HIGH TEMPERATURES.

報告者

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