47362-SE
Strategies in Enzymatic Oxidation Catalysis, at the ACS National Meeting, August 2007, Boston, MA
This report describes a symposium entitled “Strategies in Enzymatic Oxidation Catalysis” which was held at the 234th ACS National Meeting, Boston, MA, August 19-23, 2007. Prof. Giovanna Gadda (Georgia State University) and myself Prof. Justine P. Roth (Johns Hopkins University) acted as co-organizers. The symposium was sponsored by a PRF SE grant 47362-SE as well as the ACS divisions of biological chemistry (BIOL), colloids and surface science (COLL) and the catalysis secretariat (CATL).
Integration of biotechnology platforms in the petroleum field requires understanding how enzymes catalyze difficult oxidation reactions. For instance, illuminating strategies by which enzymes transform strong C–H bonds in aqueous media using molecular oxygen would facilitate “greener” approaches to the production of commodity chemicals as well as the implementation of bioreactors for environmental remediation. The symposium will cover the following subjects of fundamental importance to the petrochemical industry: (i) the mechanisms of C–H oxidation, (ii) the strategies used by enzymes to effect catalytic rate acceleration and (iii) the applications of biochemical and biophysical principles in biocatalyst engineering.
The funds from the SE grant were used to support only the international speakers. The scientists were in attendance and outlines of their presentations provided below: Profs. Roger Sheldon, Chris Schofield, Stephanie Burton and Stephen Chapman
The abstracts are included below:
Biocatalysis using phenol oxidase and peroxidases
by Burton (University of Capetown, South Africa)
This presentation will describe the application of oxidase reactions in producing selected target products using biocatalytic routes. Our research is focused on the synthesis of compounds such as antioxidants, using selected oxidase or peroxidase enzymes, and including a multi-enzyme bioprocess approach. This involves the rational design of biocatalytic routes to the target compounds, identification of suitable enzyme biocatalysts, and development of effective conditions for each step in the designed synthetic route. Optimization of each biocatalysis step, and incorporation of the steps as unit operations, allows us to develop efficient bioprocesses for the specific target products. Thus, a “tool-box” of biocatalytic reactions can be applied, including site-specific hydroxylation and oxidation, dimerisation, oligomerisation and depolymerisation.
Heme enzymes: Oxidation catalysts of precision and power
by Chapman (University of Edinburgh, UK)
Heme is arguably the most versatile cofactor in biology. Heme-containing proteins have a wide variety of functions ranging from oxygen transport to simple single-electron transfers. In catalytic terms heme-enzymes have the capacity to bind and activate molecular oxygen making them powerful oxidation catalysts. The cytochromes P450, for example, are a superfamily of monooxygenases that catalyse a wide variety of regio- and stereo-specific insertions of single oxygen atoms into organic substrates. Heme-enzymes are also capable of functioning as dioxygenases - inserting both atoms of molecular oxygen into their substrates. In this presentation two examples of heme dioxygenases will be discussed: a tryptophan-2,3,-dioxygenase from Xanthomonas campestris; and a nitric oxide dioxygenase from Rhodobacter sphaeroides. Tryptophan-2,3-dioxygenase catalyses the oxidation of L-tryptophan to N-formylkynurenine and we have recently reported the high-resolution structure of the enzyme in complex with substrate. The NO-dioxygenase catalyses the conversion of nitric oxide into nitrate. New results on the mechanisms of action of these two novel heme-enzymes will be discussed.
Green catalytic oxidations with oxidases and peroxidases
by Sheldon (Delft University of Technology, Netherlands)
Oxidases and peroxidases are synthetically interesting classes of oxidoreductases as they have no cofactor regeneration requirement and they can catalyze oxidations of a variety of substrates with the green oxidants, molecular oxygen and hydrogen peroxide, respectively. In this lecture we shall discuss the synthetic potential of two subclasses of these enzymes: the copper-dependent laccases and the haloperoxidases.
2OG Oxygenases: The most versatile of oxidising enzymes?
by Schofield (Oxford UK)
2OG oxygenases catalyze reactions with a range of important functional roles in most life-forms. Biological roles include transcriptional regulation including oxygen sensing and histone modification, DNA repair and fatty acid metabolism. In metazoans, these roles have so far all been limited to hydroxylation reactions, but in plants and micoorganisms, the 2OG oxygenases catalyze a plethora of oxidative reactions, leading to the proposal that they may be the most versatile biological oxidizing catalysts. Some 2OG oxygenase reactions are unprecedented in synthesis and include cyclizations,
ring fragmentation, C-C bond cleavage, epimerization, desaturation, and halogenations. Structural studies have revealed a conserved double-stranded beta-helix or jelly-roll platform that supports iron and 2OG binding residues. Variations on
this fold occur in sub-families; structural insights have played a key role in functional assignments. The lecture will review studies on the family focusing on chemically unusual reactions and roles of 2OG oxygenases in transcriptional regulation.
In addition to bringing together perspectives of industrial and academic scientists and engineers, the four session symposium attracted other eminent speakers from the US National Academies. These guest included Profs. Stephen Lippard, Judith Klinman and Paul Ortiz de Montellano. The symposium also gave visibility to a number new investigators including Drs. Rudi Fasan and Rajeev Prabhakar.
