BEGIN:VCALENDAR VERSION:2.0 PRODID:-//132.216.98.100//NONSGML kigkonsult.se iCalcreator 2.20.4// BEGIN:VEVENT UID:20250915T090706EDT-8618CuIvkC@132.216.98.100 DTSTAMP:20250915T130706Z DESCRIPTION:Abstract:\n\nRadical S-adenosyl-L-methionine (SAM) enzymes are currently the largest known group of metalloenzymes and catalyze an extrao rdinarily broad range of radical-mediated chemical reactions. All radical SAM enzymes are unified by the presence of an active site [Fe4S4] cluster that can reductively cleave SAM and thus initiate the catalytic cycle. Rad ical SAM enzymes are also found in the biosynthesis of nucleoside natural products with oxetanocin A and albomycin δ2 being two notable examples. Ox sB is a cobalamin-dependent radical SAM enzyme that participates in the bi osynthetic conversion of 2'-deoxyadenosine 5'-monophosphate (2'-dAMP) to t he antiviral and antibiotic agent oxetanocin A\, which contains a four-mem bered oxetane ring. Recent findings indicate that OxsB catalyzes an oxidat ive\, intramolecular C‒C bond formation in 2'-dAMP to yield a highly unsta ble bicyclic intermediate. This intermediate undergoes regioselective bond cleavage catalyzed by OxsA to afford oxetanocin A aldehyde phosphate. Alb omycin δ2 is a nucleoside antibiotic possessing a unique thiofuranose moie ty. Biosynthesis of the thiofuranose ring requires an unprecedented\, radi cal-mediated\, sulfur-for-oxygen swapping reaction catalyzed by the twitch radical SAM enzyme AbmM. Recent studies have provided evidence that the s ulfur is donated by the radical SAM [Fe4S4] cluster in this reaction. Furt hermore\, the immediate product of the AbmM catalyzed reaction undergoes a dehydration reaction involving a phosphorylated intermediate generated by the multifunctional kinase AbmG. The biosynthetic roles of these enzymes\ , their mechanisms of catalysis\, and the insights they can offer for furt hering our understanding of radical SAM enzymology will be discussed in th is presentation.\n\n \n\nBio:\n\nHun-wen (Ben) Liu was born in Taiwan and graduated with a BS degree in chemistry from Tunghai University (Taichung) in 1974. He completed his Ph.D. at Columbia University under the supervis ion of Koji Nakanishi\, where he studied the additivity relation in excito n-split circular dichroism curves and its application in structural studie s of oligosaccharides. In 1981\, he joined Christopher Walsh at MIT as a p ostdoctoral fellow\, where he became involved in mechanistic enzymology. I n 1984\, he became an assistant professor in the Department of Chemistry a t the University of Minnesota\, where he achieved the rank of Distinguishe d McKnight University Professor in 1999. Since 2000\, he has held the Geor ge H. Hitchings Regents Chair in Drug Design at the University of Texas at Austin\, where he is Professor of Medicinal Chemistry\, Chemistry\, and B iochemistry. His research lies at the crossroads of biological and organic chemistry\, with particular emphasis on enzyme reaction mechanisms\, natu ral product biosynthesis\, protein function regulation\, enzyme inhibitor design and synthesis\, and metabolic pathway engineering. His work has bee n recognized by many awards\, including the Horace S. Isbell Award (1993)\ , the Nakanishi Prize (2007)\, the Repligen Award in Chemistry of Biologic al Processes (2008)\, the A. I. Scott Medal for Excellence in Biological C hemistry Research (2011)\, the Arthur C. Cope Late Career Scholars Award ( 2014)\, and the Gordon Hammes Lectureship Award (2023)\, among many others . He is an elected fellow of the American Association for the Advancement of Science (2005)\, the American Academy of Microbiology (2006)\, and the Academia Sinica (2008). He is an active member of a number of professional societies\, and serves on many advisory boards\, review panels\, and edit orial boards.\n DTSTART:20250916T170000Z DTEND:20250916T183000Z LOCATION:OM 10\, Maass Chemistry Building\, CA\, QC\, Montreal\, H3A 0B8\, 801 rue Sherbrooke Ouest SUMMARY:Chemical Society Seminar: Ben Liu- Radical SAM Enzymes in the Biosy nthesis of Atypical Nucleoside Natural Products URL:/chemistry/channels/event/chemical-society-seminar -ben-liu-radical-sam-enzymes-biosynthesis-atypical-nucleoside-natural-3674 85 END:VEVENT END:VCALENDAR