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Research points out that in the taurine/alpha-ketoglutarate dioxygenase and the 2,4-dichlorophenoxyacetate/alphaketoglutarate dioxygenase enzymes, the iron center is proximal to the residues undergoing post-translational modifications. Data indicate that the former enzyme selects a tetrahedral substrate anion, while the latter prefers planar carboxylate, suggesting differences in the catalysis mediated by the enzymes.

Research has been conducted on the neutral uncharged sulfur dioxide complexes. The reactivity of these complexes toward the nucleophile diazomethane has been investigated and the stability and structure of the produced sulfene complexes have been examined.

Research involving the direct oxygenation of anaerobically grown crystals of isopenicillin N synthase, a non-haem iron-dependent oxidase, complexed with Fe2+ and substrates, then structural analysis by X-ray crystallography, supports the hypothesis of a two-stage reaction sequence leading to penicillin. The most simple explanation for the formation of a monocyclic sulphoxide product from delta-(L-alpha-aminoadipoyl)-L-cysteinyl-L-S-methylcysteine is the interception of a high-valency iron-oxo species.

Isopenicillin N synthase (IPNS) catalyses the four-electron oxidation of a tripeptide, l-δ-(α-aminoadipoyl)-l-cysteinyl-d-valine (ACV), to give isopenicillin N (IPN), the first-formed β-lactam in penicillin and cephalosporin biosynthesis. IPNS catalysis is dependent upon an iron(II) cofactor and oxygen as a co-substrate. In the absence of substrate, the carbonyl oxygen of the side-chain amide of the penultimate residue, Gln330, co-ordinates to the active-site metal iron. Substrate binding ablates the interaction between Gln330 and the metal, triggering rearrangement of seven C-terminal residues, which move to take up a conformation that extends the final α-helix and encloses ACV in the active site. Mutagenesis studies are reported, which probe the role of the C-terminal and other aspects of the substrate binding pocket in IPNS. The hydrophobic nature of amino acid side-chains around the ACV binding pocket is important in catalysis. Deletion of seven C-terminal residues exposes the active site and leads to formation of a new type of thiol oxidation product. The isolated product is shown by LC-MS and NMR analyses to be the ene-thiol tautomer of a dithioester, made up from two molecules of ACV linked between the thiol sulfur of one tripeptide and the oxidised cysteinyl β-carbon of the other. A mechanism for its formation is proposed, supported by an X-ray crystal structure, which shows the substrate ACV bound at the active site, its cysteinyl β-carbon exposed to attack by a second molecule of substrate, adjacent. Formation of this product constitutes a new mode of reaction for IPNS and non-heme iron oxidases in general., (© 2017 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.)