title: Biosynthesis of butirosin: transfer and deprotection of the unique amino acid side chain.
abstract: Butirosin, an aminoglycoside antibiotic produced by Bacillus circulans, bears the unique (S)-4-amino-2-hydroxybutyrate (AHBA) side chain, which protects the antibiotic from several common resistance mechanisms. The AHBA side chain is advantageously incorporated into clinically valuable antibiotics such as amikacin and arbekacin by synthetic methods. Therefore, it is of significant interest to explore the biosynthetic origins of this useful moiety. We report here that the AHBA side chain of butirosin is transferred from the acyl carrier protein (ACP) BtrI to the parent aminoglycoside ribostamycin as a gamma-glutamylated dipeptide by the ACP:aminoglycoside acyltransferase BtrH. The protective gamma-glutamyl group is then cleaved by BtrG via an uncommon gamma-glutamyl cyclotransferase mechanism. The application of this pathway to the in vitro enzymatic production of novel AHBA-bearing aminoglycosides is explored with encouraging implications for the preparation of unnatural antibiotics via directed biosynthesis.
authors.affiliation: Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, United Kingdom.
authors.forename: Nicholas M
authors.initials: NM
authors.lastname: Llewellyn
authors.forename: Yanyan
authors.initials: Y
authors.lastname: Li
authors.forename: Jonathan B
authors.initials: JB
authors.lastname: Spencer
mesh_terms: D000213:Acyl Carrier Protein / Q000378:metabolism; D000596:Amino Acids / Q000378:metabolism; D000617:Aminoglycosides / Q000378:metabolism; D001407:Bacillus / Q000201:enzymology / Q000378:metabolism*; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics; D002076:Butirosin Sulfate / Q000096:biosynthesis* / Q000737:chemistry / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics
chemical_list: D000213:Acyl Carrier Protein; D000596:Amino Acids; D000617:Aminoglycosides; D001426:Bacterial Proteins; D011994:Recombinant Proteins; D002076:Butirosin Sulfate