Sequential Enzymatic Epoxidation Involved in Polyether Lasalocid Biosynthesis
摘要:
Enantioselective epoxidation followed by regioselective epoxide opening reaction are the key processes in construction of the polyether skeleton. Recent genetic analysis of ionophore polyether biosynthetic gene dusters suggested that flavin-containing monooxygenases (FMOs) could be involved in the oxidation steps. In vivo and in vitro analyses of Lsd18, an FMO involved in the biosynthesis of polyether lasalocid, using simple olefin or truncated diene of a putative substrate as substrate mimics demonstrated that enantioselective epoxidation affords natural type mono- or bis-epoxide in a stepwise manner. These findings allow us to figure out enzymatic polyether construction in lasalocid biosynthesis.
Sequential Enzymatic Epoxidation Involved in Polyether Lasalocid Biosynthesis
摘要:
Enantioselective epoxidation followed by regioselective epoxide opening reaction are the key processes in construction of the polyether skeleton. Recent genetic analysis of ionophore polyether biosynthetic gene dusters suggested that flavin-containing monooxygenases (FMOs) could be involved in the oxidation steps. In vivo and in vitro analyses of Lsd18, an FMO involved in the biosynthesis of polyether lasalocid, using simple olefin or truncated diene of a putative substrate as substrate mimics demonstrated that enantioselective epoxidation affords natural type mono- or bis-epoxide in a stepwise manner. These findings allow us to figure out enzymatic polyether construction in lasalocid biosynthesis.
Our recent findings of the first epoxide hydrolase Lsd19, involved in lasalocid A biosynthesis, led us to investigate a long-standing controversial issue on the mechanism of enzymatic epoxide-opening cascades. The site-directed mutagenesis and domain dissection analysis to reveal the mechanism of the reaction catalyzed by Lsd19 is examined, especially in the role of acidic amino acid pair and catalytic
Recently, we reported that the epoxide hydrolase Lsd19, the first enzyme shown to catalyze epoxide-opening cascades, can catalyze the conversion of a putative bisepoxide intermediate to polyether antibiotic lasalocid, which involves energetically disfavored 6-endo-tet cyclization of the epoxy alcohol. Here, we examined the substrate tolerance of Lsd19. Lsd19 accepts various substrate analogues differing in the left segment of lasalocid and epoxide stereochemistry to afford either THF-THP or THF-THF products with excellent regioselectivity.