title: 7alpha-OH epimerisation of bile acids via oxido-reduction with Xanthomonas maltophilia.
abstract: The microbial 7alpha-OH epimerisation of cholic, chenodeoxycholic, and 12-ketochenodeoxycholic acids (7alpha-OH bile acids) with Xanthomonas maltophilia CBS 827.97 to corresponding 7beta-OH derivatives with scarcity of oxygen is described. With normal pressure of oxygen the 7-OH oxidation products are obtained. No biotransformations are achieved in anaerobic conditions. The microbial 7alpha-OH epimerisation is achieved by oxidation of 7-OH function and subsequent reduction. Partial purification, in fact, of the enzymatic fraction revealed the presence of two hydroxysteroid dehydrogenases (HSDH) alpha- and beta-stereospecific together with a glycocholate hydrolase. On the basis of these results a further application is the microbial reduction of 6alpha-fluoro and 6beta-fluoro-3alpha-hydroxy-7-oxo-5beta-cholan-24-oic acid methyl esters to the corresponding 7alpha-OH and 7beta-OH derivatives.
authors.affiliation: Dipartimento di Chimica, Università di Ferrara, Via L. Borsari 46, I-44100, Ferrara, Italy. mda@dns.unife.it
authors.forename: Alessandro
authors.initials: A
authors.lastname: Medici
authors.forename: Paola
authors.initials: P
authors.lastname: Pedrini
authors.forename: Ercolina
authors.initials: E
authors.lastname: Bianchini
authors.forename: Giancarlo
authors.initials: G
authors.lastname: Fantin
authors.forename: Alessandra
authors.initials: A
authors.lastname: Guerrini
authors.forename: Benedetto
authors.initials: B
authors.lastname: Natalini
authors.forename: Roberto
authors.initials: R
authors.lastname: Pellicciari
mesh_terms: D001647:Bile Acids and Salts / Q000737:chemistry* / Q000378:metabolism; D003840:Deoxycholic Acid / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000737:chemistry*; D006913:Hydroxysteroid Dehydrogenases / Q000378:metabolism; D008956:Models, Chemical; D010100:Oxygen / Q000378:metabolism; D013053:Spectrophotometry; D020615:Stenotrophomonas maltophilia / Q000378:metabolism*; D014580:Ursodeoxycholic Acid / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000737:chemistry
chemical_list: C450847:6-fluoro-3,7-dihydroxy-5-cholan-24-oic acid; C092780:6-fluoro-ursodeoxycholic acid; D001647:Bile Acids and Salts; D003840:Deoxycholic Acid; D014580:Ursodeoxycholic Acid; D006913:Hydroxysteroid Dehydrogenases; D010100:Oxygen