. "Forms part of the penicillin biosynthesis pathway." . "Epimerization at C-5 of the 5-amino-5-carboxypentanoyl group to form penicillin N is required to make a substrate for EC 1.14.20.1, to produce cephalosporins." . . . "Isopenicillin-N epimerase" . "Isopenicillin N = penicillin N." . "Pyridoxal 5'-phosphate" .