Penicillin, cephalosporins, and cephamycins are two out of five of the naturally occurring β-lactam antibiotics that contain the β-lactam ring. Penicillin is used to treat bacterial infections and is prevalently used by doctors to treat infections like streptococcal upper respiratory tract infections, scarlet fever, and erysipelas infections. Cephamycins and (very similar) cephalosporins on the other hand used for the treatment of severe bacterial infections like urinary tract infection, blood infection, bone and joint infection, and lower respiratory tract infection. They are all produced in different steps in the same biosynthesis pathway. This pathway shows the biosynthesis of penicillin, cephalosporin, and cephamycin in the bacteria Streptomyces cattleya. The pathway shows the production of penicillin by branching out at isopenicillin N to form penicillin using the enzyme beta-lactamase class A-like protein-containing pyridoxal 5'-phosphate as a cofactor and eventually penicillioic acid and 6-aminopenicillanic acid. The pathway then branches out at the intermediate deacetylcephalosporin C to eventually synthesize cephamycin C through a couple of cephalosporin intermediates and the enzyme CmcI hydroxylase. It also branches off and leads to the synthesis of cephalosporin C through the enzyme deacetylcephalosporin-C acetyltransferase.

Penicillin and Cephalosporin Biosynthesis References