Reaction Coordinate of Isopenicillin N Synthase: Oxidase versus Oxygenase Activity
- 15 January 2010
- journal article
- research article
- Published by American Chemical Society (ACS) in Biochemistry
- Vol. 49 (6), 1176-1182
- https://doi.org/10.1021/bi901772w
Abstract
Isopenicillin N synthase (IPNS) can have both oxidase and oxygenase activity depending on the substrate. For the native substrate, ACV, oxidase activity exists; however, for the substrate analogue ACOV, which lacks an amide nitrogen, IPNS exhibits oxygenase activity. The potential energy surfaces for the O−O bond elongation and cleavage were calculated for three different reactions: homolytic cleavage via traditional Fenton chemistry, heterolytic cleavage, and nucleophilic attack. These surfaces show that the hydroperoxide−ferrous intermediate, formed by O2-activated H atom abstraction from the substrate, can exploit different reaction pathways and that interactions with the substrate govern the pathway. The hydrogen bonds from hydroperoxide to the amide nitrogen of ACV polarize the σ* orbital of the peroxide toward the proximal oxygen, facilitating heterolytic cleavage. For the substrate analogue ACOV, this hydrogen bond is no longer present, leading to nucleophilic attack on the substrate intermediate C−S bond. After cleavage of the hydroperoxide, the two reaction pathways proceed with minimal barriers, resulting in the closure of the β-lactam ring for the oxidase activity (ACV) or formation of the thiocarboxylate for oxygenase activity (ACOV).Keywords
This publication has 26 references indexed in Scilit:
- Transition States in a Protein Environment − ONIOM QM:MM Modeling of Isopenicillin N SynthesisJournal of Chemical Theory and Computation, 2008
- The Mechanism for Isopenicillin N Synthase from Density-Functional Modeling Highlights the Similarities with Other Enzymes in the 2-His-1-carboxylate FamilyBiochemistry, 2007
- Protein Environment Facilitates O2 Binding in Non-Heme Iron Enzyme. An Insight from ONIOM Calculations on Isopenicillin N Synthase (IPNS)The Journal of Physical Chemistry B, 2007
- VTVH-MCD and DFT Studies of Thiolate Bonding to {FeNO}7/{FeO2}8 Complexes of Isopenicillin N Synthase: Substrate Determination of Oxidase versus Oxygenase Activity in Nonheme Fe EnzymesJournal of the American Chemical Society, 2007
- Oxygen Activation by the Noncoupled Binuclear Copper Site in Peptidylglycine α-Hydroxylating Monooxygenase. Reaction Mechanism and Role of the Noncoupled Nature of the Active SiteJournal of the American Chemical Society, 2004
- X-ray absorption studies of the ferrous active site of isopenicillin N synthase and related model complexesBiochemistry, 1993
- X-ray absorption spectroscopic studies of the high-spin iron(II) active site of isopenicillin N synthase: evidence for iron-sulfur interaction in the enzyme-substrate complexBiochemistry, 1992
- Thiolate ligation of the active site iron(II) of isopenicillin N synthase derives from substrate rather than endogenous cysteine: spectroscopic studies of site-specific Cys .fwdarw. Ser mutated enzymesBiochemistry, 1992
- The biosynthesis of penicillins and cephalosporinsNatural Product Reports, 1988
- Stepwise ring closure in penicillin biosynthesis. Intitial β-lactam formationJournal of the Chemical Society, Chemical Communications, 1984