Publications

• A new family of iron-dependent halogenases acts on freestanding substrates.

  Hillwig M.L., Liu X.

  Regio- and stereospecific incorporation of a halogen atom to an unactivated sp(3) carbon in a freestanding molecule is a challenging transformation that is currently missing in the inventory of enzyme-mediated reactions. Here we report what is to our knowledge the first example of a nonheme iron e ... >> More

  Regio- and stereospecific incorporation of a halogen atom to an unactivated sp(3) carbon in a freestanding molecule is a challenging transformation that is currently missing in the inventory of enzyme-mediated reactions. Here we report what is to our knowledge the first example of a nonheme iron enzyme (WelO5) in the welwitindolinone biosynthetic pathway that can monochlorinate an aliphatic carbon in 12-epi-fischerindole U and 12-epi-hapalindole C, substrates that are free from peptidyl or acyl carrier protein. << Less

  Nat Chem Biol 10:921-923(2014) [PubMed] [EuropePMC]

  This publication is cited by 1 other entry.

• Aliphatic Halogenase Enables Late-Stage C-H Functionalization: Selective Synthesis of a Brominated Fischerindole Alkaloid with Enhanced Antibacterial Activity.

  Zhu Q., Hillwig M.L., Doi Y., Liu X.

  The anion promiscuity of a newly discovered standalone aliphatic halogenase WelO5 was probed and enabled the selective synthesis of 13R-bromo-12-epi-fischerindole U via late-stage enzymatic functionalization of an unactivated sp(3) C-H bond. Pre-saturating the WelO5 active site with a non-native b ... >> More

  The anion promiscuity of a newly discovered standalone aliphatic halogenase WelO5 was probed and enabled the selective synthesis of 13R-bromo-12-epi-fischerindole U via late-stage enzymatic functionalization of an unactivated sp(3) C-H bond. Pre-saturating the WelO5 active site with a non-native bromide anion was found to be critical to the highly selective in vitro transfer of bromine, instead of chlorine, to the target carbon center and also allowed the relative binding affinity of bromide and chloride towards the WelO5 enzyme to be assessed. This study further revealed the critical importance of halogen substitution on modulating the antibiotic activity of fischerindole alkaloids and highlights the promise of WelO5-type aliphatic halogenases as enzymatic tools to fine-tune the bioactivity of complex natural products. << Less

  Chembiochem 17:466-470(2016) [PubMed] [EuropePMC]

  This publication is cited by 1 other entry.

• Discovery of a Promiscuous Non-Heme Iron Halogenase in Ambiguine Alkaloid Biogenesis: Implication for an Evolvable Enzyme Family for Late-Stage Halogenation of Aliphatic Carbons in Small Molecules.

  Hillwig M.L., Zhu Q., Ittiamornkul K., Liu X.

  The elucidation of enigmatic enzymatic chlorination timing in ambiguine indole alkaloid biogenesis led to the discovery and characterization of AmbO5 protein as a promiscuous non-heme iron aliphatic halogenase. AmbO5 was shown capable of selectively modifying seven structurally distinct ambiguine, ... >> More

  The elucidation of enigmatic enzymatic chlorination timing in ambiguine indole alkaloid biogenesis led to the discovery and characterization of AmbO5 protein as a promiscuous non-heme iron aliphatic halogenase. AmbO5 was shown capable of selectively modifying seven structurally distinct ambiguine, fischerindole and hapalindole alkaloids with chlorine via late-stage aliphatic C-H group functionalization. Cross-comparison of AmbO5 with a previously characterized aliphatic halogenase homolog WelO5 that has a restricted substrate scope led to the identification of a C-terminal sequence motif important for substrate tolerance and specificity. Mutagenesis of 18 residues of WelO5 within the identified sequence motif led to a functional mutant with an expanded substrate scope identical to AmbO5, but an altered substrate specificity from the wild-type enzymes. These observations collectively provide evidence on the evolvable nature of AmbO5/WelO5 enzyme duo in the context of hapalindole-type alkaloid biogenesis and implicate their promise for the future development of designer biocatalysis for the selective late-stage modification of unactivated aliphatic carbon centers in small molecules with halogens. << Less

  Angew Chem Int Ed Engl 55:5780-5784(2016) [PubMed] [EuropePMC]

  This publication is cited by 1 other entry.