Department of Biotechnology, Delft University of Technology, Van der Maasweg 9, 2629, HZ, Delft, The Netherlands.
Present address: Faculty of Science, Utrecht University, Budapestlaan 6, 3584 CD, Utrecht, The Netherlands.
ChemSusChem. 2019 Jul 5;12(13):3192-3203. doi: 10.1002/cssc.201801862. Epub 2018 Nov 5.
Epimerization of cholic and chenodeoxycholic acid (CA and CDCA, respectively) is a notable conversion for the production of ursodeoxycholic acid (UDCA). Two enantiocomplementary hydroxysteroid dehydrogenases (7α- and 7β-HSDHs) can carry out this transformation fully selectively by specific oxidation of the 7α-OH group of the substrate and subsequent reduction of the keto intermediate to the final product (7β-OH). With a view to developing robust and active biocatalysts, novel NADH-active 7β-HSDH species are necessary to enable a solely NAD -dependent redox-neutral cascade for UDCA production. A wild-type NADH-dependent 7β-HSDH from Lactobacillus spicheri (Ls7β-HSDH) was identified, recombinantly expressed, purified, and biochemically characterized. Using this novel NAD -dependent 7β-HSDH enzyme in combination with 7α-HSDH from Stenotrophomonas maltophilia permitted the biotransformations of CA and CDCA in the presence of catalytic amounts of NAD , resulting in high yields (>90 %) of UCA and UDCA.
胆酸和鹅脱氧胆酸（CA 和 CDCA，分别）的差向异构化是生产熊去氧胆酸（UDCA）的重要转化。两种对映体互补的羟甾脱氢酶（7α-和 7β-HSDH）可以通过特异性氧化底物的 7α-OH 基团，随后将酮中间产物还原为最终产物（7β-OH），完全选择性地进行这种转化。为了开发稳健且活性高的生物催化剂，需要新型的 NADH 活性 7β-HSDH 种类，以实现仅依赖 NAD 的氧化还原中性级联反应，用于 UDCA 的生产。从乳杆菌 spicheri（Ls7β-HSDH）中鉴定、重组表达、纯化和生物化学表征了一种野生型 NADH 依赖性 7β-HSDH。在催化量的 NAD 的存在下，使用这种新型的 NAD 依赖性 7β-HSDH 酶与嗜麦芽窄食单胞菌的 7α-HSDH 相结合，使得 CA 和 CDCA 能够进行生物转化，生成高收率（>90%）的 UCA 和 UDCA。
