Reconstitution of the peptidoglycan cytoplasmic precursor biosynthetic pathway in cell-free system and rapid screening of antisense oligonucleotides for Mur enzymes.

Bacterial peptidoglycan is the cell wall component responsible for various biological activities. Its cytoplasmic precursor UDP-N-acetylmuramyl pentapeptide is biosynthesized by the first six enzymes of peptidoglycan synthetic pathways (Mur enzymes), which are all proved to be important targets for antibiotic screening. In our present work, the genes encoding Mur enzymes from Escherichia coli were co-expressed in the cell-free protein synthesis (CFPS) system, and the activities of Mur enzymes derived from CFPS system were validated by the synthesis of the final product UDP-N-acetylmuramyl pentapeptide. Then this in vitro reconstituted Mur biosynthetic pathway was used to screen a panel of specific antisense oligonucleotides for MurA and MurB. The selected oligonucleotides were proved to eliminate the expression of Mur enzymes, and thus inhibit the Mur biosynthetic pathway. The present work not only developed a rapid method to reconstruct and regulate a biosynthetic pathway in vitro, but also may provide insight into the development of novel antibiotics targeting on peptidoglycan biosynthetic pathway.