A gene encoding a dye-linked d-amino acid dehydrogenase (Dye-DADH) homologue was found in a hyperthermophilic archaeon, Sulfurisphaera tokodaii. The predicted amino acid sequence suggested that the gene product is a membrane-bound type enzyme. The gene was overexpressed in Escherichia coli, but the recombinant protein was exclusively produced as an inclusion body. In order to avoid production of the inclusion body, an expression system using the thermoacidophilic archaeon Sulfolobus acidocaldarius instead of E. coli as the host cell was constructed. The gene was successfully expressed in Sulfolobus acidocaldarius, and its product was purified to homogeneity and characterized. The purified enzyme catalyzed the dehydrogenation of various d-amino acids, with d-phenylalanine being the most preferred substrate. The enzyme retained its full activity after incubation at 90 °C for 30 min and after incubation at pH 4.0–11.0 for 30 min at 50 °C. This is the first report on membrane-bound Dye-DADH from thermophilic archaea that was successfully expressed in an archaeal host.

在嗜热古细菌Sulfurisphaera tokodaii中发现了一个编码染料连接的d-氨基酸脱氢酶（Dye-DADH）同源物的基因。预测的氨基酸序列表明该基因产物是膜结合型酶。该基因在大肠杆菌中过表达，但重组蛋白仅作为包涵体产生。为了避免产生包涵体，构建了使用嗜热嗜酸古细菌Sulfolobus acidocaldarius代替大肠杆菌作为宿主细胞的表达系统。该基因已成功地在Sulfolobus acidocaldarius中表达，并将其产物纯化至均质并进行表征。纯化的酶催化各种d-氨基酸的脱氢，其中d-苯丙氨酸是最优选的底物。该酶在90°C孵育30分钟后以及在pH 4.0–11.0在50°C孵育30分钟后仍保持其全部活性。这是关于嗜热古细菌膜结合染料-DADH的首次报道，该染料在古细菌宿主中成功表达。