Penicillin biosynthesis: multiple pathways from a modified substrate

Preparations of the enzyme isopenicillin N synthetase from Cephalosporium acremonium CO 728 convert the modified tripeptide substrate δ-(L-α-aminoadipoyl)-L-cysteingyl-D-allylgycine into penam, homoceph-3-em, hydroxycepham, and hydroxyhomocepham type products; these have been isolated and their structures established.