Characterization of Methyltransferase from Apramycin Biosynthetic Gene Cluster and Improvement Production of Apramycin in Engineered Streptoalloteichus Tenebrarius

Abstract

BackgroundApramycin is a structurally unique aminoglycoside, used in veterinary medicine or the treatment of Salmonella, Escherichia coli and Pasteurella multocida infections in farm. Although discovered and used many years ago, many biosynthetic steps of apramycin are still obscure. ResultsIn this study, we identified a HemK family methyltransferase, aprI, involved in apramycin biosynthesis. The function of aprI was studied by using gene disruption and biochemical experiments, and a new aminoglycoside antibiotic demethyl-apramycin was purified from aprI disruption strain. Experiments proved that AprI converted demethyl-aprosamine to aprosamine in vitro. Based on this, the apramycin production strain was improved by overexpression the AprI to decrease the impurity production. ConclusionsWe have identified aprI is a 7’-N-methyltransferase gene in apramycin biosynthesis and confirmed the substrate of methyltransferase. Engineering of aprI resulted in a strain producing a new aminoglycoside demethyl-apramycin and apramycin mono-producing strain with less impurity production. Finally, the yield of demethyl-apramycin in apramycin mono-producing strain decreased from 196±36 mg/L to 51±9 mg/L, and the yield of apramycin increased from 2227±320 mg/L to 2331±210 mg/L.