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Atypical regioselective biohydrolysis on steroidal oxiranes by Aspergillus niger whole cells: Some stereochemical features

2007; Elsevier BV; Volume: 72; Issue: 8 Linguagem: Inglês

10.1016/j.steroids.2007.04.003

1878-5867

Fabricio R. Bisogno, Alejandro A. Orden, Celeste Aguirre Pranzoni, Diego A. Cifuente, Óscar S. Giordano, Marcela Kurina‐Sanz,

Enzyme Catalysis and Immobilization

5,6-Epoxycholestan-3β-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 α and β 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.