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Characterization of Enzymes Involved in Butane Metabolism from the Pollutant Degrading bacterium, Pseudomonas butanovora John Stenberg John Stenberg Mentor:

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Presentation on theme: "Characterization of Enzymes Involved in Butane Metabolism from the Pollutant Degrading bacterium, Pseudomonas butanovora John Stenberg John Stenberg Mentor:"— Presentation transcript:

1 Characterization of Enzymes Involved in Butane Metabolism from the Pollutant Degrading bacterium, Pseudomonas butanovora John Stenberg John Stenberg Mentor: Dan Arp, Ph.D. Mentor: Dan Arp, Ph.D. September 1, 2004 September 1, 2004

2 Bioremediation  As the world population and the demands of agriculture and industry increase, the availability of fresh water continues to decrease  The problems associated with depleted or polluted water affect not only humans, but the plant and animal populations we depend upon  The solution?  Bioremediation: The process by which living organisms act to degrade hazardous organic contaminants or transform hazardous inorganic contaminants to environmentally safe levels in soils, subsurface materials, water, sludges, and residues.

3 Cometabolism  Definition: the transformation of a non-growth-supporting substrate by a microorganism  Pseudomonas butanovora contains a multi-component monooxygenase that is able to catalyze the degradation of many substrates including trichloroethylene, dichloroethylenes, aromatic structures, and others  Such compounds are not only environmental pollutants, but in many cases, are very stable  Once oxidized by a monooxygenase, it is much easier for these compounds to be further degraded H Cl C Cl Trichloroethylene (TCE) H O Cl C Cl TCE epoxide Ex. Trichloroethylene oxidation

4 Pseudomonas butanovora  Isolated in Japan from activated sludge near an oil refinery  Capable of growth with butane via the oxidation of butane to 1-butanol as the first step in the terminal oxidation pathway C 4 H 10 + O 2 C 4 H 9 OH + H 2 O  Also capable of growth with other alkanes (C2–C9), alcohols (C2–C4) and organic acids as sources of carbon and energy  Growth on alkanes catalyzed by a soluble butane monooxygenase (sBMO)

5 Butane Monooxygenase (sBMO) Butane Terminal Oxidation Pathway of Pseudomonas butanovora Example: butane to butyric acid (further metabolized as fatty acid) 1-Butanol Alcohol Dehydrogenases Butyraldehyde Butyric Acid Aldehyde Dehydrogenases

6 Butane monooxygenase  Responsible for oxidation of butane C 4 H 10 + O 2 C 4 H 9 OH + H 2 O C 4 H 10 + O 2 C 4 H 9 OH + H 2 O  Three part enzyme 1. Hydroxylase component (BMOH) - contains the substrate binding di-iron active site and is responsible for the oxidation of butane to 1-butanol 2. Reductase component (BMOR) - responsible for the transfer of electrons from NADH+H + to the hydroxylase component 3. Component B (BMOB) 3. Component B (BMOB) - coupling protein required for substrate oxidation, electron transfer ??

7 Proposed Catalytic Cycle of BMO Adapted from Wallar, B.J. and J.D. Lipscomb, 1996, Chem. Rev. 96: 2625-2657

8 BMO Research Objectives  Purification and characterization of BMO components Reductase Reductase Hydroxylase Hydroxylase  BMO Activity Methane oxidation Methane oxidation

9 Steps leading to Purification  1. Grow Pseudomonas butanovora cells Sealed flasks, carboys Sealed flasks, carboys Butane 7% overpressure Butane 7% overpressure  2. Harvest cells through centrifugation  3. Prepare cell-free extract Lysis by freeze/thaw and sonication Lysis by freeze/thaw and sonication Centrifuge at 46,000 x g Centrifuge at 46,000 x g

10 Enzyme Purification  Multiple column process 1. Q Sepharose resin column (anion exchange purification) 2. 2 nd Q Sepharose column 3. Gel filtration Superdex 75 – reductase Sephacryl S-300 - hydroxylase  What so far? -Purified reductase with activity -Partially purified hydroxylase with activity Pharmacia FPLC System

11 sBMO Reductase Purification 97.4 45 66.2 31 21.5 14.4 CFE Q1 Q2 S 75

12 Purified Reductase Fractions Reductase Properties A 270/458 ratio: 3.1 - 3.7, which is similar to the methane monoxygenase reductase and other purified oxygenase reductases A 458/340 ratio: 1.4, also similar to the methane monoxygenase reductase UV/Visible Spectra has maxima at 272, 340, ~ 400, 458 nm Reductase UV/Visible Spectra

13 Step DCPIP Reduction (µmol min -1 mg protein -1) Fold Purification Cell Free Extract 5.8 ± 0.1 1 Q1 44 ± 0.8 8 Q2 86 ± 1.5 15 Superdex 75 115 ± 1.4 20 Reductase activity and fold purification

14 BMOH Hydroxylase Purification 1st Q Sepharose Column Spectra

15 M Q1 Q2S-300 97.4 45 66.2 31 21.5 14.4    Hydroxylase Purification Steps

16 Step EO production (nmol min -1 mg protein -1) % Recovery Whole Cell 300100 Cell Free Extract 10635 1 st Q Sepharose Column 23177 BMO Hydroxylase activity during initial purification steps  Measured by ethylene oxide (EO) production by gas chromatography

17 Methane Oxidation  Methanol Production  5 picomol min -1 mg protein -1

18 Progress  Mass culturing at 5 L/carboy is repeatable allowing for ~7-8 g of cell mass/carboy with high BMO activity  Recoverable BMO hydroxylase activities in cell free extracts and initial chromotography steps at high activity comparable to published sMMO purification strategy of Fox et al. (1989)  BMO reductase purified to homogeneity with demonstrated activity; comparable to the sMMO system reductase in activity and spectral characteristics  Possible methane oxidation

19 Acknowledgements  Howard Hughes Medical Institute  Daniel Arp, Ph.D.  Brad Dubbels, Ph.D.  Arp Lab  Kevin Ahern, Ph.D.


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