以silaffin引導仿生矽化固定Rhodosporidium toruloides D型胺基酸氧化酶

Immobilization of Rhodosporidium toruloides D-amino acid oxidase via silaffin-mediated biomimetic silicification

王信富(Shin-Fu Wang)

指導教授 ： 官宜靜

大同大學/工程學院/生物工程學系所/碩士(2012年)

摘要

生物矽化(biosilicification)在自然界是一個常見的現象。經由生物矽化產生的氧化矽，為自然界中僅次於碳酸鈣的生物礦物。地球上絕大部份的生物矽化出現於簡單的水中生物包括單細胞生物像矽藻、放射蟲和褐藻以及多細胞的海綿等。在矽藻Cylindrotheca fusiformis中，經高度轉譯後修飾的胜肽稱作silaffin能協助二氧化矽直接沉積於細胞壁。不過，未修飾的silaffin於常溫和常壓下，也能於生物體外的水溶液中起始二氧化矽的聚合。於本研究中，以大腸桿菌表現Rhodosporidum toruloides D型胺基酸氧化酶和silaffin R1或R2胜肽的融合蛋白- RtDAOR1H和RtDAOR2H，以自行催化進行仿生矽化作用。相對於未融合固定前，經固定後之RtDAOR1H和RtDAOR2H的Tm值分別提升8和9oC，對過氧化氫耐受性之半衰期亦分別延長為13.3倍和9.6倍，經過重複使用10次，其殘存活性仍約有80%。

關鍵字

D型胺基酸 ； 仿生矽化

並列摘要

Biosilicification is one of the common phenomenon in nature. Silica generated from this process is the second most abundant biomineral, only next to calcium carbonate. The majority of biosilicification on earth occurs in simple aquatic life forms including unicellular organisms such as diatom, radiolarian and synurophytes as well as multicellular sponges. In the diatom Cylindrotheca fusiforms, heavily post-translationally modified peptides called silaffins can asist direct silica deposition on the cell wall. However the unmodified silaffin is also capable of initiating in vitro silica polycondensation in aqueous solution at ambient temperature and pressure. In this study, fusion proteins of Rhodosporidium toruloides D-amino acid oxidase and R1 or R2 peptide, RtDAOR1H and RtDAOR2H, expressed in Escherichia coli can self-catalyze the biomimetic silicification. As compared to free RtDAO, Tm values for immobilized RtDAOR1H and RtDAOR2H were 8 and 9oC higher. The half-lives for resistance to hydrogen peroxide of immobilized RtDAOR1H and RtDAOR2H were increased by 13.3 and 9.6 folds. After 10 repeated cycles of operation, the residual activity of bilized RtDAOR1H and RtDAOR2H were still above 80%.

並列關鍵字

D-amino acid ； silicification ； silaffin

參考文獻

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