| 摘要 |
7-beta -hydroxysteroid dehydrogenase (7beta -HSDH) and its derived functional equivalents, obtainable from bacterium, preferably Collinsella aerofaciensstrain DSM 3979 (ATCC 25986), are claimed. Independent claims are also included for: (1) a 7-beta -HSDH with an amino acid sequence having 263 amino acid residues (SEQ ID NO: 2) or its derived sequence with a degree of identity of at least 80% to the sequence of SEQ ID NO: 2; (2) enzymatic synthesis of 7-beta -hydroxysteroids, comprises reacting the corresponding 7-keto steroids in presence of the 7-beta -HSDH, and optionally isolating at least one reduction product, from the reaction preparation; (3) enzymatic oxidation of 7-beta -hydroxysteroids, comprises reacting the 7-beta -hydroxysteroids in presence of 7-beta -hydroxysteroid dehydrogenase, and optionally isolating the formed oxidation product, from the reaction preparation; and (4) preparing ursodeoxycholic acid derivative of formula (I), comprising (a) optionally chemically oxidizing cholic acid derivative of formula (II) to dehydrocholic acid derivative of formula (III), (b) reducing (III) in presence of at least one 7-beta -HSDH, to 3,12-diketo-7-beta -cholanic acid derivative of formula (IV), (c) reducing (IV) in presence of at least one 3-alpha -hydroxysteroid dehydrogenase (3-alpha -HSDH) to corresponding 12-keto-ursodeoxycholic acid derivative of formula (V), (d) chemically reducing (V) to (I), and (e) optionally further purifying the reaction product. R : alkyl, NR 1>R 2>, H, alkali metal ion or N(R 3>) 4+>; R 3> : H or alkyl; and R 1>, R 2> : not defined. [Image] [Image] [Image]. |
