Further studies on microbiological ring-expansion of penicillin N.

Abstract

The rate of microbiological ring-expansion of penicillin N to deacetoxycephalosporin C using protoplast lysates of the antibiotic-negative mutant Cephalosporium acremonjum M-0198 was increased some 70-fold over that of an earlier system. The stimulatory effects of FeSO4 and ascorbate described by Hook et al. were confirmed; the optimum concentrations found were 0.04 mM FeSO4 and 0.67 mM ascorbate. ATP concentration was lowered to 0.83 mM; phosphoenolpyruvate and pyruvate kinase were eliminated. The optimum pH and temperature for the reaction were 7.2 and 25.degree. C, respectively. .alpha.-Ketoglutarate and MnCl2 showed no marked effect on the reaction, MgSO4 and KCl were mildly stimulatory, and CuSO4 and ZnSO4 were very inhibitory. Penicillin N was optimal at a concentration of 0.07 mM. Specific ring-expansion activity reached its peak 13 h after growth ceased and then disappeared rapidly.