- Enzymatic α/β Inversion of C-3 Hydroxyl of Bile Acids and Study of the Effects of Organic Solvents on Reaction Rates
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Enzymatic α/β inversion of the C-3 hydroxyl of numerous bile acids containing different numbers of hydroxyl groups in the skeleton and side chains of different lengths has been carried out.Inversion was obtained in two steps through the sequential use of the commercial enzymes 3α- and 3β-hydroxysteroid dehydrogenase, employed in the free form or immobilized on Eupergit C.The transformations were practically quantitative and the products more than 98percent pure.NAD was regenerated in situ with the pyruvate/lactic dehydrogenase system and NADH with the formate/formate dehydrogenase system.The effects of product inhibition on reaction rates and the favorable effects produced by low concentrations (7-10percent, v/v) of ethyl acetate and ethanol were also examined.
- Riva, Sergio,Bovara, Roberto,Zetta, Lucia,Pasta, Piero,Ottolina, Gianluca,Carrera, Giacomo
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- Two-way enantioselective control in the epoxidation of alkenes with the keto bile acid-Oxone system
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A number of 3-keto bile acid derivatives has been prepared and evaluated in the asymmetric epoxidation of unfunctionalized olefins with Oxone. The control of the enantioselectivity with the production of both enantiomers is strictly regulated by the bile acid inductor, as a function of substitution at carbons C(7) or C(12). Up to 98% ee has been achieved. The stereochemical outcome of the reaction may be rationalized in terms of spiro transition state model.
- Bortolini, Olga,Fantin, Giancarlo,Fogagnolo, Marco,Mari, Lara
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p. 4482 - 4490
(2007/10/03)
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- Regiospecific oxidoreductions catalyzed by a new Pseudomonas paucimobilis hydroxysteroid dehydrogenase
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The preparative-scale regio- and stereo-specific oxidation of hydroxy groups and reduction of keto functions at C(3) of several C21 bile acids, catalyzed by a new 3α-hydroxysteroid dehydrogenase (3α-HSDH) is reported. The crude enzyme, isolated from the cells of Pseudomonas paucimobilis, revealed the presence of a further enzymatic fraction containing a secondary alcohol dehydrogenase (SADH), that has been used to recycle the cofactor.
- Bianchini, Ercolina,Chinaglia, Nicola,Dean, Mariangela,Giovannini, Pier Paolo,Medici, Alessandro,Pedrini, Paola,Poli, Silvia
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p. 1391 - 1398
(2007/10/03)
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- Bile acid transformations by Alcaligenes recti
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Metabolism of cholic acid, chenodeoxycholic acid, ursodeoxycholic acid, and deoxycholic acid by the grown cells of the bacterium Alcaligenes recti suspended in water was studied.Each isolated metabolite was characterized by the application of various spectroscopic methods.Cholic acid, chenodeoxycholic acid, ursodeoxycholic acid, and deoxycholic acid yielded methylated derivatives 3α-methoxy-7α,12α-dihydroxy-5β-cholanoic acid, 3α-methoxy-7α-hydroxy-5β-cholanoic acid, 3α-methoxy-7β-hydroxy-5β-cholanoic acid, and 3α-methoxy-12α-hydroxy-5β-cholanoic acid, respectively.In addition, cholic acid furnished 7α,12α-dihydroxy-3-oxochol-4-en-24-oic acid; chenodeoxycholic acid gave 7α-hydroxy-3-oxo-5β-cholanoic acid and 7α-hydroxy-3-oxochol-4-en-24-oic acid while ursodeoxycholic acid yielded 7β-hydroxy-3-oxochol-4-en-24-oic acid and 3-oxochola-4,6-dien-24-oic acid.The formation of various metabolites showed that two competitive enzymic reactions, i.e., selective methylation of the 3α-hydroxy group and dehydrogenation in the A/B rings, were operative.The methylation process was found to be enzymic involving an S-adenosyl-L-methionine (AdoMet)-dependent methyl transferase, and this reaction appeared to be inhibitory to the process of degradation of the ring system.In the other reaction sequence, degradation of the ring system was initiated by dehydrogenation of the 3α-hydroxy group.A 7β-dehydratase activity producing the Δ6 double bond was also noticeable in the metabolism of ursodeoxycholic acid. Keywords: sterols; bile acids; metabolites; microbial transformation; Alcaligenes recti; bacterial transformation
- Mazumder, Ipsita,Mahato, Shashi B.
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