Polyketide synthase thioesterases catalyze rapid hydrolysis of peptidyl thioesters
作者:Meng Wang、Peter Opare、Christopher N. Boddy
DOI:10.1016/j.bmcl.2009.01.040
日期:2009.3
Polyketide synthase (PKS) thioesterases (TEs) catalyze the macrocyclization of linear acyl chains into macrolactones. Herein we show that peptide based substrates are processed by PKS TEs with greater catalytic efficiency than more native like acyl substrates. This result strengths the link between PKS and non-ribosomal peptide synthetase systems and provides a new tool for studying PKS TEs. (C) 2009 Elsevier Ltd. All rights reserved.
Unraveling Terminal C-Domain-Mediated Condensation in Fungal Biosynthesis of Imidazoindolone Metabolites
作者:Stuart W. Haynes、Brian D. Ames、Xue Gao、Yi Tang、Christopher T. Walsh
DOI:10.1021/bi2004922
日期:2011.6.28
The fungal peptidyl alkaloids of the tryptoquialanine and fumiquinazoline families are nonribosomally assembled by annulation of the indole side chain of fumiquinazoline F (FQF) with an alaninyl or aminoisobutyryl unit by monomodular NRPS enzymes containing adenylation, thiolation, and condensation (A-T-C) domains. The Af12060 and Af12050 enzyme pair from Aspergillus fumigatus thereby converts FQF to FQA, while the homologous TqaH and TqaB enzyme pair from Penicillium aethiopicum makes the 2'-epi diastereomer of FQA, differing only in the stereochemistry of one of the C-N bonds formed in the annulation with L-Ala. To evaluate the basis for this stereochemical control, we have mixed and matched the flavoprotein oxygenases Af12060 and TqaH with the A-T-C modular enzymes Af12050 and TqaB to show that the NRPS enzymes control the stereochemical outcome. The terminal 50 kDa condensation domains of Af12050 and TqaB are solely responsible for the stereochemical control as shown both by making chimeric (e.g., A-T-C* and A*-T*-C) forms of these rnonomodular NRPS enzymes and by expression, purification, and assay of the excised C-domains. The Af12050 and TqaB condensation domains are thus a paired set of diastereospecific annulation catalysts that act on the fumiquinazoline F scaffold.