Characterization of the Enzyme BtrD from Bacillus circulans and Revision of Its Functional Assignment in the Biosynthesis of Butirosin

摘要

The 2-deoxystreptamine(2-DOS)-containing aminoglycosides are a clinically important class of antibiotics, whose members include neomycin, gentamycin, and the semisynthetic amikacin. A detailed understanding of the biosynthetic enzymes that construct these natural products is required for the rational engineering of biosynthetic pathways to produce novel aminoglycosides. Butirosin (5) is a 2-DOS aminoglycoside that contains a novel (S)-4-amino-2-hydroxybutyrate side chain. In 2005, Kudo et al.[1] proposed that BtrD, a protein encoded by the butirosin gene cluster,[2] functions as a nucleotidyltransferase that specifically synthesizes thymidine 5-diphosphoglucosamine (TDP-GlcN) from thymidine 5-triphosphate (TTP) and glucosamine-1-phosphate, thus generating the sugar donor for a putative glycosyltransferase, BtrM (Scheme 1 a). It was also proposed that homologous enzymes in other gene clusters also function as hexose-1-phosphate nucleotidyltransferases.