Biological transformation of kanamycin A to amikacin (BBK-8).

(Fig. 1).3) Butirosin (Fig. 2) has the L-HABA structure as an acylated side chain on its 2-deoxystreptamine molecule. The structural analogies between AMK and BTR suggest that AMK could be formed by feeding KMA to a broth culture of B. circulars. Recent reports on the biosynthesis of BTR4•5) indicate that the coupling of L-HABA to the ribostamycin (RBT) molecule (Fig. 2) could be one of the last steps in the biosynthesis of BTR. The parent strain of B. circulars was found to be sensitive to KMA at 5 10 ƒÊg/ml. A KMA resistant strain of B. circulars was obtained by stepwise enrichment in liquid culture at KMA concentrations of 600-800 ƒÊg/ml. Therefore, the KMA-resistant strain was further mutageniz-