College of Pharmacy
“Never give up.”
Zheng graduated from Peking University in 2012 with a M.S. in Pharmaceutics and gained experience in formulation and drug delivery. Currently she is a fourth year graduate student in the Van Lanen lab at University of Kentucky. Her thesis project focuses on elucidating the biosynthetic mechanism of the nucleoside antibiotic muraymycin.
THE BIOSYNTHETIC MECHANISM OF THE ANTIBIOTIC MURAYMYCIN
BACKGROUND: Muraymycin is a lipopeptidyl nucleoside antibiotic produced by Streptomyces sp. NRRL30471. Muraymycin exhibits remarkable antibiotic activity against gram-positive and gram-negative bacteria by inhibiting MraY translocase, an essential enzyme involved in the biosynthesis of peptidoglycan cell walls. Similar to several members of this antibiotic family that includes A-90289 and muraminomicin, the structure of muraymycin consists of a disaccharide comprised of two modified ribofuranose units linked by an O-β (1 → 5) glycosidic bond; however, muraymycin holds the distinction in that one ribose is alkylated to be a 2-OMe sugar. Prior work has identified the gene cluster involved in the biosynthesis of muraymycin. However, the enzymatic mechanism of the muraymycin scaffold assembly has not been elucidated.
OBJECTIVES: Our long-term research goal is to delineate the biosynthetic pathway of muraymycin in order to develop analogues through chemoenzymatic synthesis and mutasynthesis. Our current goal is to study the function of enzymes for the biosynthesis of muraymycin disaccharide scaffold.
METHODS: To interrogate the enzyme mechanism of the biosynthesis of disaccharide scaffold of muraymycin, six enzymes were cloned and expressed in Escherichia coli BL21 (DE3) or Streptomyces lividans TK24. Activity tests were performed, and HPLC analysis and LC-MS analysis were utilized to identify the product(s).
RESULTS: Six enzymes are now functionally assigned and characterized: Mur16, a non-heme, Fe(II)-dependent α-ketoglutarate: UMP dioxygenase; Mur17, an L-threonine: uridine-5’-aldehyde transaldolase; Mur20, an L-methionine:1-aminotransferase; Mur26, a low specificity pyrimidine nucleoside phosphorylase; Mur18, a primary amine-requiring nucleotidylyltransferase; Mur19, a 5-amino-5-deoxyribosyltransferase. A one pot enzyme reaction was utilized to produce two disaccharide analogs of muraymycin scaffold.