Precursor-directed biosynthesis: biochemical basis of the remarkable selectivity of the erythromycin polyketide synthase toward unsaturated triketides.
The structural basis for the striking stereochemical discrimination among triketide analogs has been investigated by incubating a series of N-acetyl cysteamine (-SNAC) esters of unsaturated triketides with DEBS module 2+TE. The triketide analogs were first screened under a standard set of short-term incubation conditions in the presence of the extender substrate methylmalonyl-CoA and NADPH. For those triketide analogs that served as substrates for module 2+TE, the relative specificity, represented by the k(cat)/K(M) values, was quantitated. Triketide diastereomers that were converted in precursor-directed biosynthesis experiments to unsaturated 16-membered ring macrolides by DEBS(KS1(0)) were good to excellent substrates for DEBS module 2+TE, whereas analogs that were converted to the 14-membered ring analogs of 10,11-dehydro-6-deoxyerythronolide B by DEBS(KS1(0)) were not turned over at all by module 2+TE.
Cane
David E
DE
Department of Chemistry, Box H, Brown University, Providence, RI 02912, USA. david_cane@brown.edu
Kudo
Fumitaka
F
Kinoshita
Kenji
K
Khosla
Chaitan
C
D001667:Binding, Competitive; D004917:Erythromycin / Q000096:biosynthesis*; D007700:Kinetics; D009097:Multienzyme Complexes / Q000737:chemistry* / Q000378:metabolism; D011498:Protein Precursors / Q000096:biosynthesis / Q000378:metabolism; D016930:Saccharopolyspora / Q000378:metabolism; D013379:Substrate Specificity
D009097:Multienzyme Complexes; D011498:Protein Precursors; D004917:Erythromycin