Structure of a cephalosporin synthase.
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.
Valegård
K
K
Department of Biochemistry, Uppsala University, Sweden.
van Scheltinga
A C
AC
Lloyd
M D
MD
Hara
T
T
Ramaswamy
S
S
Perrakis
A
A
Thompson
A
A
Lee
H J
HJ
Baldwin
J E
JE
Schofield
C J
CJ
Hajdu
J
J
Andersson
I
I
D003001:Cloning, Molecular; D018360:Crystallography, X-Ray; D004926:Escherichia coli; D005296:Ferrous Compounds / Q000737:chemistry; D019751:Intramolecular Transferases / Q000737:chemistry*; D007656:Ketoglutaric Acids / Q000737:chemistry; D008958:Models, Molecular; D010088:Oxidoreductases / Q000737:chemistry; D010100:Oxygen / Q000737:chemistry; D046915:Penicillin-Binding Proteins; D011487:Protein Conformation; D013302:Streptomyces / Q000201:enzymology
D005296:Ferrous Compounds; D007656:Ketoglutaric Acids; D046915:Penicillin-Binding Proteins; D010088:Oxidoreductases; C038370:isopenicillin N synthetase; D019751:Intramolecular Transferases; C038371:deacetoxycephalosporin C synthetase; D010100:Oxygen