Key Laboratory of Biorheological Science and Technology, Ministry of Education, College of Bioengineering, Chongqing University, Chongqing 400030, China.
Chongqing Key Laboratory of Medicinal Resources in the Three Gorges Reservoir Region, School of Biological & Chemical Engineering, Chongqing University of Education, Chongqing 400067, China.
Protein Sci. 2019 May;28(5):910-919. doi: 10.1002/pro.3599. Epub 2019 Mar 22.
7α-Hydroxysteroid dehydrogenase (7α-HSDH) is an NAD(P)H-dependent oxidoreductase belonging to the short-chain dehydrogenases/reductases. In vitro, 7α-HSDH is involved in the efficient biotransformation of taurochenodeoxycholic acid (TCDCA) to tauroursodeoxycholic acid (TUDCA). In this study, a gene encoding novel 7α-HSDH (named as St-2-1) from fecal samples of black bear was cloned and heterologously expressed in Escherichia coli. The protein has subunits of 28.3 kDa and a native size of 56.6 kDa, which suggested a homodimer. We studied the relevant properties of the enzyme, including the optimum pH, optimum temperature, thermal stability, activators, and inhibitors. Interestingly, the data showed that St-2-1 differs from the 7α-HSDHs reported in the literature, as it functions under acidic conditions. The enzyme displayed its optimal activity at pH 5.5 (TCDCA). The acidophilic nature of 7α-HSDH expands its application environment and the natural enzyme bank of HSDHs, providing a promising candidate enzyme for the biosynthesis of TUDCA or other related chemical entities.
7α-羟甾体脱氢酶（7α-HSDH）是一种 NAD(P)H 依赖性氧化还原酶，属于短链脱氢酶/还原酶。在体外，7α-HSDH 参与牛磺鹅去氧胆酸（TCDCA）向牛磺熊去氧胆酸（TUDCA）的有效生物转化。在这项研究中，从黑熊粪便样本中克隆并异源表达了一种编码新型 7α-HSDH（命名为 St-2-1）的基因。该蛋白亚基为 28.3 kDa，天然大小为 56.6 kDa，表明为同源二聚体。我们研究了该酶的相关性质，包括最适 pH、最适温度、热稳定性、激活剂和抑制剂。有趣的是，数据表明 St-2-1 与文献中报道的 7α-HSDHs 不同，因为它在酸性条件下发挥作用。该酶在 pH 5.5（TCDCA）时表现出最佳活性。7α-HSDH 的嗜酸性质扩展了其应用环境和 HSDHs 的天然酶库，为 TUDCA 或其他相关化学实体的生物合成提供了一种有前途的候选酶。
