More than just a halogenase: modification of fatty acyl moieties by a trifunctional metal enzyme.
The highly selective oxidative halogenations by non-heme iron and α-ketoglutarate-dependent enzymes are key reactions in the biosynthesis of lipopeptides, and often bestow valuable bioactivity to the metabolites. Here we present the first biochemical characterization of a putative fatty acyl halogenase, HctB, which is found in the hectochlorin biosynthetic pathway of Lyngbya majuscula. Its unprecedented three-domain structure, which includes an acyl carrier protein domain, allows self-contained conversion of the covalently tethered hexanoyl substrate. Structural analysis of the native product by (13) C NMR reveals high regioselectivity but considerable catalytic promiscuity. This challenges the classification of HctB as a primary halogenase: along with the proposed dichlorination, HctB performs oxygenation and an unprecedented introduction of a vinyl-chloride moiety into the nonactivated carbon chain. The relaxed substrate specificity is discussed with reference to a molecular model of the enzyme-substrate complex. The results suggest that fatty acyl transformation at the metal center of HctB can bring about considerable structural diversity in the biosynthesis of lipopeptides.
Institute of Biotechnology and Biochemical Engineering, Graz University of Technology, Petersgasse 12, 8010 Graz (Austria).
Sarah M
SM
Pratter
Jakov
J
Ivkovic
Ruth
R
Birner-Gruenberger
Rolf
R
Breinbauer
Klaus
K
Zangger
Grit D
GD
Straganz
D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism*; D001665:Binding Sites; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D000458:Cyanobacteria / Q000201:enzymology; D007783:Lactones / Q000737:chemistry / Q000378:metabolism; D008666:Metalloendopeptidases / Q000737:chemistry / Q000378:metabolism*; D008670:Metals / Q000737:chemistry / Q000378:metabolism; D062105:Molecular Docking Simulation; D013379:Substrate Specificity; D013844:Thiazoles / Q000737:chemistry / Q000378:metabolism
D001426:Bacterial Proteins; D007783:Lactones; D008670:Metals; D013844:Thiazoles; C454807:hectochlorin; D008666:Metalloendopeptidases
halogenation; metalloenzymes; molecular diversity; natural products; non-heme iron