title: Regioselective Acetylation of C21 Hydroxysteroids by the Bacterial Chloramphenicol Acetyltransferase I.
abstract: Chloramphenicol acetyltransferase I (CATI) detoxifies the antibiotic chloramphenicol and confers a corresponding resistance to bacteria. In this study we identified this enzyme as a steroid acetyltransferase and designed a new and efficient Escherichia-coli-based biocatalyst for the regioselective acetylation of C21 hydroxy groups in steroids of pharmaceutical interest. The cells carried a recombinant catI gene controlled by a constitutive promoter. The capacity of the whole-cell system to modify different hydroxysteroids was investigated, and NMR spectroscopy revealed that all substrates were selectively transformed into the corresponding 21-acetoxy derivatives. The biotransformation was optimized, and the reaction mechanism is discussed on the basis of a computationally modeled substrate docking into the crystal structure of CATI.
authors.affiliation: Institute of Biochemistry, Saarland University, Campus B2.2, 66123 Saarbrücken (Germany).
authors.forename: Azzam
authors.initials: A
authors.lastname: Mosa
authors.affiliation: Center for Bioinformatics, Saarland University, Campus E2.1, 66123 Saarbrücken (Germany).
authors.forename: Michael C
authors.initials: MC
authors.lastname: Hutter
authors.affiliation: Institute of Pharmaceutical Biology, Saarland University, Campus C2.2, 66123 Saarbrücken (Germany).
authors.forename: Josef
authors.initials: J
authors.lastname: Zapp
authors.affiliation: Institute of Biochemistry, Saarland University, Campus B2.2, 66123 Saarbrücken (Germany).
authors.forename: Rita
authors.initials: R
authors.lastname: Bernhardt
authors.affiliation: Institute of Biochemistry, Saarland University, Campus B2.2, 66123 Saarbrücken (Germany). f.hannemann@mx.uni-saarland.de.
authors.forename: Frank
authors.initials: F
authors.lastname: Hannemann
mesh_terms: D000107:Acetylation; D055162:Biocatalysis; D001711:Biotransformation; D002701:Chloramphenicol / Q000378:metabolism; D015500:Chloramphenicol O-Acetyltransferase / Q000737:chemistry / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology*; D005947:Glucose / Q000494:pharmacology; D006914:Hydroxysteroids / Q000737:chemistry* / Q000378:metabolism*; D062105:Molecular Docking Simulation; D011487:Protein Conformation; D013237:Stereoisomerism; D013379:Substrate Specificity
chemical_list: D006914:Hydroxysteroids; D002701:Chloramphenicol; D015500:Chloramphenicol O-Acetyltransferase; D005947:Glucose
keywords: acetylation; biotransformations; chloramphenicol acetyltransferases; regioselectivity; steroids