- Pactamycin, produced by the soil bacterium Streptomyces pactum, is a cytotoxic antibiotic that belongs to the aminocyclitol family of natural products. This antibiotic has shown various forms of biological activity, including antibacterial, antifungal, antimalarial, and antitumor activities. Despite its outstanding biological activity, the mode of formation of its pharmacophore (the aminocyclitol unit) remains elusive. The PtmN (an oxidoreductase) and PtmA (an aminotransferase) proteins are hypothesized to be involved in the initial steps in the biosynthesis of the aminocyclitol unit. The ptmA and ptmN genes were cloned into the pRSET B expression vector and transferred into Escherichia coli BL21 pLysS. SDS-PAGE gel electrophoresis showed that the transformed E. coli strains were able to produce soluble PtmA or PtmN. Crude extracts of the bacterial cells containing soluble PtmA or PtmN proteins were tested for their enzymatic activity. HPLC was used to analyze the products. The results showed that a new compound was produced in the reaction containing PtmA and PtmN. However, the identity of the product has not been established. Further experimentation is needed to confirm the activity of the enzyme.