Preparing tauroursodeoxycholic acid (TUDCA) using a double-enzyme-coupled system

Tauroursodeoxycholic acid (TUDCA) has been used to treat many diseases effectively. TUDCA generation in vivo is a complex process involving five steps catalyzed by five enzymes in the enterohepatic circulation of bile salt. In this paper, we report a novel in vitro TUDCA preparation technology in which the epimerization of taurochenodeoxycholic acid (TCDCA) to TUDCA is directly catalyzed by immobilized 7α- and 7β-hydroxysteroid dehydrogenases (7α- and 7β-HSDH) in a double-enzyme-coupled system. One pair of oxidoreductases from Clostridium absonum DSM599, which was made up of 7α- and 7β-HSDH, was immobilized on a modified chitosan microsphere by separate immobilization and co-immobilization. The protein loading yields of 7α- and 7β-HSDH were 79.06% and 87.18%, and their activity yields were 57.23% and 53.97%, respectively. In the batch-wise reactions catalyzed by double-enzyme-coupled system, 72.76% of the TCDCA was transformed, and only 22.08% TUDCA was obtained on the basis of separate immobilization. The TUDCA yield was 62.49% under the catalytic effects of co-immobilized 7α- and 7β-HSDH microspheres, while it was only 41.23% based on the mixture of separate immobilized 7α- and 7β-HSDH microspheres. The enzyme catalytic technology described in this paper offers a potential application for synthesizing TUDCA and other high-value bile acid derivatives in vitro.