| abstract |
A peptide precursor of the ACV (aminoadipyl- cysteinylvaline) type, in which the valine moiety may be replaced by any readily available amino acid may be converted into a cephalosporin of the typen where R, is H, lower alkyl or functionalized carboxylic group and R 2 is H or lower alkyl, by reacting the precursor with novel cyclase, epimerase and ring expansion enzymes isolated from a cell-free extract of a prokaryotic organism such as Streptomyces clavuligerus. The three novel enzymes may be immobilized separately or together on a suitable support medium and the conversion may be carried out in a continuous mode. |