Heterologous Expression of Epoxomicin in Escherichia coli

Epoxomicin is an epoxyketone proteasome inhibitor with synthetic derivatives approved or under investigation for treatment of multiple myeloma. To leverage the advantages of Escherichia coli as a rapidly growing and readily engineered host for the production of epoxomicin and analogues, we expressed codon-optimized versions of the epoxomicin biosynthetic genes, epxD, epxE, and epxF. Epoxomicin was detected, but the major product was a ketone resulting from α,β-keto acid precursor decarboxylation. Epoxomicin yield was improved by altering the copy numbers of each gene and creating a fusion of epxE and epxF. Our optimized system offers promise for efficient engineering and biosynthesis of improved epoxomicin analogues.