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Catalytic Site Atlas

CSA LITERATURE entry for 1w2n

E.C. namedeacetoxycephalosporin-C synthase
SpeciesStreptomyces clavuligerus (Bacteria)
E.C. Number (IntEnz) 1.14.20.1
CSA Homologues of 1w2nThere are 54 Homologs
CSA Entries With UniProtID P18548
CSA Entries With EC Number 1.14.20.1
PDBe Entry 1w2n
PDBSum Entry 1w2n
MACiE Entry M0137

Literature Report

IntroductionDeacetoxycephalosporin C synthase (DAOCS) from Streptomyces clavuligerus is able to catalyse the synthesis of sporins from penicillin using 2-oxoglutarate as a cosubstrate. This reaction is potentially very useful to industry because it enables processing of penicillin to other beta-lactam ring containing compounds which may not trigger antibiotic resistance systems in prokaryotes that evolved with penicillin itself as the selective agent. As with the other members of the family of 2OG utilising enzymes, DAOCS shows a beta barrel catalytic core and has its iron centre ligated to two histidines and an aspartate residue at the active site. It also displays roughly the same catalytic cycle, albeit for a specific reaction, as seen for the other members of the family, such as Anthocyanidin synthase.
MechansimThere are two half reactions that occur in the enzyme which are independent in as much as they can be uncoupled under certain conditions. In the oxidative half reaction the Fe (II) centre binds to dioxygen, acting as a nucleophile thus becoming oxidised to Fe (III). This creates a peroxide radical which reacts with the 2OG bound to the iron causing decarboxylation and the further oxidation of iron to the highly reactive Fe (IV) species with a double bond to oxygen. In the reductive half reaction the double bonded oxygen accepts a hydrogen atom from the beta methyl group of penicillin to form an OH group liganded to the iron (now Fe (III)) and an alkyl radical. The alkyl radical reacts with the sulphur of the ring to cause the expansion of the ring and the migration of the radical electron to the 2C of the ring. From here, hydrogen transfer to the OH group via the Sulphur atom occurs leading to the formation of a double bond between the 2C and the 3C of the ring, and the formation of Fe (II) bonded to a water molecule. This completes the reaction cycle. Arg 74 ensures that the hydrogen transfer can occur by sterically constraining penicillin so that it is in the same plane as the Fe (IV) double bonded oxygen.
Reaction

Catalytic Sites for 1w2n

Annotated By Reference To The Literature - Site 3 (Perform Site Search)
ResidueChainNumberUniProtKB NumberFunctional PartFunctionTargetDescription
ArgA7474macie:sideChainSterically constrains the penicillin substrate thus positioning it in the optimal position for hydrogen transfer.

Literature References

Notes:
Oster LM
Conformational flexibility of the C terminus with implications for substrate binding and catalysis revealed in a new crystal form of deacetoxycephalosporin C synthase.
J Mol Biol 2004 343 157-171
PubMed: 15381427
ValegÄrd K
The structural basis of cephalosporin formation in a mononuclear ferrous enzyme.
Nat Struct Mol Biol 2004 11 95-101
PubMed: 14718929
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