Structure of a cephalosporin synthase.

Journal article

Penicillins and cephalosporins are among the most widely used therapeutic agents. These antibiotics are produced from fermentation-derived materials as their chemical synthesis is not commercially viable. Unconventional steps in their biosynthesis are catalysed by Fe(II)-dependent oxidases/oxygenases; isopenicillin N synthase (IPNS) creates in one step the bicyclic nucleus of penicillins, and deacetoxycephalosporin C synthase (DAOCS) catalyses the expansion of the penicillin nucleus into the nucleus of cephalosporins. Both enzymes use dioxygen-derived ferryl intermediates in catalysis but, in contrast to IPNS, the ferryl form of DAOCS is produced by the oxidative splitting of a co-substrate, 2-oxoglutarate (alpha-ketoglutarate). This route of controlled ferryl formation and reaction is common to many mononuclear ferrous enzymes, which participate in a broader range of reactions than their well-characterized counterparts, the haem enzymes. Here we report the first crystal structure of a 2-oxoacid-dependent oxygenase. High-resolution structures for apo-DAOCS, the enzyme complexed with Fe(II), and with Fe(II) and 2-oxoglutarate, were obtained from merohedrally twinned crystals. Using a model based on these structures, we propose a mechanism for ferryl formation.

Authors: Valegård, K; van Scheltinga, A; Lloyd, MD; Hara, T; Ramaswamy, S

• Publication status: Published
• Journal: Nature
• Volume: 394
• Issue: 6695
• Pages: 805-809
• Publication date: 1998-08-01
• DOI: 10.1038/29575
• EISSN: 1476-4687
• ISSN: 0028-0836
• Language: English
• Keywords: Intramolecular Transferases; Models, Molecular; Oxygen; Oxidoreductases; Escherichia coli; Crystallography, X-Ray; Penicillin-Binding Proteins; Protein Conformation; Ferrous Compounds; Ketoglutaric Acids; Streptomyces; Cloning, Molecular