Fig. 4.

Gene cluster and compartmentalization of the cephalosporin biosynthesis pathway. a Genes located in chromosome VII encoding transporters and enzymes for the early steps of the pathway are shown at the left side. Genes for late enzymes, located in chromosome II are shown at the right side. b Steps of the cephalosporin C pathway, indicating in red letters the precursors, intermediates and final product. The enzymes/genes are shown at the right side. Peroxisomes are shown as a green circle in which the enzymes involved in isopenicillin N epimerization are included. In the peroxisomal membrane a red ellipse indicates the CefP protein involved in isopenicillin N import, and an orange ellipse shows the CefM protein for penicillin N export. The cytoplasmic membrane is highlighted in purple and the CefT protein, for cephalosporin C secretion, in a blue ellipse