樟芝短鏈脫氫酶／還原酶之序列分析與蛋白質結構模擬

樟芝(Antrodia cinnamomea)爲早期台灣原住民使用來做爲治病與保健的傳統中藥，許多研究報告已經證實樟芝具有許多珍貴醫藥價值的成分，然而目前對於樟芝的細胞生理調控和代謝產物生合成仍然所知有限。本研究由樟芝表達序列標籤(expressed sequence tags)資料庫裡選殖出一個短鏈脫氫酶／還原酶(short-chain dehydrogenase/reductase; SDR)基因，命名爲ACSDR，其全長爲876個鹼基對(base pair)，可轉錄爲291個胺基酸，分子量約29.9Kda。分析ACSDR胺基酸序列找到SDR家族的保守序列(conserved residues)TGxxxGxG和預測的酵素活性催化三角(catalytic triad) Ser-Tyr-Lys。經蛋白質結構模擬計算，ACSDR以典型的α/β摺疊組成的Rossmann摺疊呈現，惟α2、β2、β3及β4構成的結構單元(domain)與其他SDR蛋白質有明顯結構差異，顯見ACSDR可能在樟芝特有的受質具有專一選擇性。在親源演化分析結果也發現，ACSDR雖然與其他真菌SDR蛋白質歸屬一群，但演化上仍有距離，顯見此蛋白質卻有可能參與樟芝特有代謝產物之生合成。因此本研究除了可以幫助了解樟芝SDR蛋白質特性與結構，也提供此蛋白質在未來代謝體工程和酵素產業上的應用價值。

關鍵字

樟芝；脫氫酶；還原酶；蛋白質結構

並列摘要

The basidiomycetous fungi Antrodia cinnamomea is often used in Traditional Chinese Medicine and is known to possess a wide range of biological activities. Here, a novel short-chain dehydrogenase reductase (SDR) gene was obtained from expressed sequence tags (ESTs) from A. cinnamomea named ACSDR. The full-length of this gene has an 876 bp open reading frame (ORF) encoding 291 amino acids with a molecular weight of 35.5 kDa. ACSDR contains a SDR family conserved residues (TGxxxGxG) and a Ser-Tyr-Lys catalytic triad. According to the protein structural modeling, the predicted ACSDR protein displays the highly similar α/β folding of typical Rossmannfold. However, a lid like domain of ACSDR formed by α2、β2、β3 and β4 reveals distinct conformation from other SDR proteins implies it's substrate specificity in A. cinnamomea. The phylogenetic analysis also showed the evolutional variant of ACSDR from other fungi SDRs. This is the first SDR identified and characterized in A. cinnamoniea, the study of ACSDR provide the further application for enzymatic industrial and metabolic engineering.

並列關鍵字

Antrodia cinnamomea ； dehydrogenase ； reductase, protein structure

國際替代計量

樟芝短鏈脫氫酶／還原酶之序列分析與蛋白質結構模擬

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