Repression and inhibition of cephalosporin synthetases in Streptomyces clavuligerus by inorganic phosphate.

Cephalosporin production by growing cells of Streptomyces clavuligerus was reduced by 100 mM inorganic phosphate. Resting cell production was repressed by prior growth in high phosphate and inhibited by phosphate. The cell-free activity of desacetoxycephalosporin C synthetase (ring expansion activity) was repressed by prior growth in high phosphate and inhibited by phosphate. Isopenicillin N synthetase (cyclase) was inhibited but not repressed. Penicillin epimerase was neither inhibited nor repressed by phosphate.