Structural highlights
Publication Abstract from PubMedIn contrast to stilbene biosynthesis by type III polyketide synthase in plants, in bacteria stilbene is produced by the collaboration of two enzymes in Photorhabdus luminescens: the unusual beta-ketosynthase StlD catalyzes the condensation of the beta-ketoacyl starter with an alpha,beta-unsaturated-acyl substrate (two C-C bond-forming reactions) to produce isopropylstyrylcyclohexanedione, which is subsequently converted to stilbene by the aromatase StlC. Here we report the in vitro characterizations of StlD and StlC, and the X-ray crystal structures of StlD. Interestingly, structure-based mutagenesis demonstrated that His302, within the conserved Cys-His-Asn triad, is not essential for the enzyme reaction, while Glu154 functions as a base-catalyst to activate the beta-ketoacyl intermediate bound to the catalytic Cys126. The structures also revealed the presence of a putative nucleophilic water molecule activated by hydrogen bond networks with Glu154 and Ser340, suggesting that StlD employs novel catalytic machinery for the condensation of two acyl substrates to produce the cyclohexanedione scaffold. Structural Insight into the Enzymatic Formation of Bacterial Stilbene.,Mori T, Awakawa T, Shimomura K, Saito Y, Yang D, Morita H, Abe I Cell Chem Biol. 2016 Dec 22;23(12):1468-1479. doi:, 10.1016/j.chembiol.2016.10.010. Epub 2016 Nov 17. PMID:27866911[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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