Purification and characterization of cloned isopenicillin N synthetase

Isopenicillin N synthetase (IPS) cloned from Cephalosporium acremonium has been isolated from transformed Escherichia coli and purified to homogeneity. The resulting, abundant, recombinant protein, whilst undergoing slightly different N-terminal processing to that observed for the fungally-derived protein, has identical kinetics for the conversion of LLD-aminoadipoyl-cysteinyl-valine to isopenicillin N. Recombinant IPS converts analogue substrates into unusual beta-lactam antibiotics in exactly the same way as the fungal protein.