title: Atypical regioselective biohydrolysis on steroidal oxiranes by Aspergillus niger whole cells: some stereochemical features.
abstract: 5,6-Epoxycholestan-3beta-ol derivatives were hydrolyzed in a diastereoconvergent manner by growing and resting cells of several strains of Aspergillus niger, particularly A. niger ATCC 11394. These strains displayed opposite regioselectivity toward each isomer in an alpha and beta epoxide mixture, thus, the nucleophilic attack took place at the less substituted and the most substituted carbon atom on each diasteromer, respectively. These biocatalysts opened trisubstituted oxiranes but were unable to hydrolyze the disubstituted oxiranes in the tested sterol derivatives. These findings suggest that A. niger strains possess another hydrolytic ability different from the commercial A. niger epoxide hydrolase (EH) that did not accept this kind of steroidal oxiranes as substrates.
authors.affiliation: INTEQUI-CONICET, Area de Química Orgánica, Facultad de Química, Bioquímica y Farmacia, UNSL, Chacabuco y Pedernera, 5700 San Luis, Argentina.
authors.forename: Fabricio R
authors.initials: FR
authors.lastname: Bisogno
authors.forename: Alejandro A
authors.initials: AA
authors.lastname: Orden
authors.forename: Celeste Aguirre
authors.initials: CA
authors.lastname: Pranzoni
authors.forename: Diego A
authors.initials: DA
authors.lastname: Cifuente
authors.forename: Oscar S
authors.initials: OS
authors.lastname: Giordano
authors.forename: Marcela
authors.initials: M
authors.lastname: Kurina Sanz
mesh_terms: D001234:Aspergillus niger / Q000378:metabolism*; D001711:Biotransformation; D004851:Epoxide Hydrolases / Q000378:metabolism*; D004852:Epoxy Compounds / Q000737:chemistry*; D005027:Ethylene Oxide / Q000737:chemistry* / Q000378:metabolism; D006868:Hydrolysis; D007700:Kinetics; D008958:Models, Molecular; D015394:Molecular Structure; D013237:Stereoisomerism
chemical_list: D004852:Epoxy Compounds; D004851:Epoxide Hydrolases; D005027:Ethylene Oxide