title: Uncovering the enzymes that catalyze the final steps in oxytetracycline biosynthesis.
abstract: Tetracyclines are a group of natural products sharing a linearly fused four-ring scaffold, which is essential for their broad-spectrum antibiotic activities. Formation of the key precursor anhydrotetracycline 3 during oxytetracycline 1 biosynthesis has been previously characterized. However, the enzymatic steps that transform 3 into 1, including the additional hydroxylation at C5 and the final C5a-C11a reduction, have remained elusive. Here we report two redox enzymes, OxyS and OxyR, are sufficient to convert 3 to 1. OxyS catalyzes two sequential hydroxylations at C6 and C5 positions of 3 with opposite stereochemistry, while OxyR catalyzes the C5a-C11a reduction using F420 as a cofactor to produce 1. The crystal structure of OxyS was obtained to provide insights into the tandem C6- and C5-hydroxylation steps. The substrate specificities of OxyS and OxyR were shown to influence the relative ratio of 1 and tetracycline 2.
authors.affiliation: Department of Chemical and Biomolecular Engineering, University of California Los Angeles, Los Angeles, California 90095, USA.
authors.forename: Peng
authors.initials: P
authors.lastname: Wang
authors.forename: Ghader
authors.initials: G
authors.lastname: Bashiri
authors.forename: Xue
authors.initials: X
authors.lastname: Gao
authors.forename: Michael R
authors.initials: MR
authors.lastname: Sawaya
authors.forename: Yi
authors.initials: Y
authors.lastname: Tang
mesh_terms: D000900:Anti-Bacterial Agents / Q000378:metabolism*; D001426:Bacterial Proteins / Q000378:metabolism*; D008958:Models, Molecular; D010088:Oxidoreductases / Q000378:metabolism*; D010118:Oxytetracycline / Q000378:metabolism*; D013302:Streptomyces / Q000201:enzymology* / Q000378:metabolism
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D010088:Oxidoreductases; D010118:Oxytetracycline