| 摘要 |
<p>12alpha -Hydroxysteroid dehydrogenase (12alpha -HSDH) mutant catalyzing at least stereospecific enzymatic oxidation of a 12-hydroxysteroid to the corresponding 12-ketosteroid, is new, where the mutant exhibits an increased specific activity (U/mg) in the presence of NADP +>cofactor in comparison to non-mutated enzyme. Independent claims are included for: (1) a nucleic acid sequence encoding the 12alpha -HSDH mutant; (2) an expression cassette comprising the nucleic acid sequence under the genetic control of at least one regulatory nucleic acid sequence; (3) a vector comprising at least one expression cassette; (4) a recombinant microorganism which carries at least one nucleic acid sequence or at least one expression cassette or is transformed with at least one vector; (5) enzymatic synthesis of 12alpha -hydroxysteroids, comprising reacting the corresponding 12-ketosteroid in the presence of 12alpha -HSDH mutant, and optionally isolating at least one reduction product formed from the reaction mixture; (6) enzymatic oxidation of 12alpha -hydroxysteroids, comprising reacting the hydroxysteroid in the presence of 12alpha -hydroxysteroid dehydrogenase, and optionally isolating an oxidation product formed from the reaction mixture; and (7) preparing ursodeoxycholic acid of formula (I), comprising oxidizing a cholic acid of formula (II) in the presence of 12alpha -hydroxysteroid dehydrogenase mutant for the corresponding 12-ketochenodeoxycholic acid of formula (III), and subsequently reacting (III) by deoxygenation to chenodeoxycholic acid of formula (IV), chemically oxidizing (IV) in position 7 to 7-keto-lithocholic acid of formula (V), reducing (V) and optionally further purifying the reaction product. R : alkyl, NR1R2, H, alkali metal ion or N(R3) 4+>; R3 : H or alkyl; and R1a : H or acyl. [Image] [Image] ACTIVITY : Hepatotropic; Litholytic. MECHANISM OF ACTION : None given.</p> |
