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Houk-Jung Organic Colloquium 247: Hung-Wen Liu

Organic Colloquium

May 4, 2023 4:00 pm - 5:00 pm
Mani L. Bhaumik Centennial Collaboratory
607 Charles E. Young Dr., East
Los Angeles, CA 90095 United States
Speaker Prof. Hung-Wen Liu


Liu Flyer

Atypical Reactions in the Biosynthesis of Herbicidins

Abstract: Herbicidins are adenosine-derived nucleoside antibiotics with an unusual tricyclic core structure. Deletion of the genes responsible for formation of the tricyclic skeleton in Streptomyces sp. L-9-10 reveals the in vivo importance of Her4, Her5 and Her6 during the early stages of herbicidin biosynthesis. In vitro characterization of Her4 and Her5 demonstrates their involvement in an initial, two stage Cā€“C coupling reaction that results in net C5′-glycosylation of ADP/ATP by UDP/TDP-glucuronic acid. Biochemical analyses and intermediate trapping experiments imply a non-canonical mechanism of C-glycosylation reminiscent of NAD-dependent S-adenosylhomocysteine hydrolase. Structural characterization of the isolated metabolites suggested possible reactions catalyzed by Her6 and Her7, and subsequent biochemical experiments confirmed the functions of Her6 and Her7 as the C3ā€™ epimerase and C8ā€™ reductase, respectively. An overall herbicidin biosynthetic pathway is thus established based on these observations.

Prof. Hung-Wen Liu

Organic Colloquium

Department of Chemistry and College of Pharmacy

University of Texas, Austin