Activity of squalene-hopene cyclases in bicontinuous microemulsions.
The paper at hand deals with biocatalysis in bicontinuous microemulsions. The latter consist of a dynamic network of oil and water domains separated by a monolayer of surfactant molecules, i.e. the interfacial layer. A microemulsion with the composition buffer--n-octane--nonionic surfactant was tested as reaction medium for an enzyme-catalysed reaction with a focus on the conversion of hydrophobic substrates, which are difficult to convert in aqueous buffer solutions. For the study at hand, we chose to investigate the activity of the squalene-hopene cyclase from Alicyclobacillus acidocaldarius (AacSHC) towards its natural substrate squalene in bicontinuous microemulsions. Firstly, the study revealed that the activity of AacSHC depends linearly on the enzyme concentration. Secondly, a hyperbolic curve was found for the dependence of the activity on the substrate concentration and a saturation of the AacSHC at substrate concentrations above 20mM was observed. Thirdly, the composition of the interfacial layer was found to have no significant influence on the activity or on the conformation of AacSHC. Surprisingly and unexpectedly, a distinctly enhanced selectivity towards hopene was discovered in the microemulsion. To conclude, bicontinuous microemulsions were found to be a suitable reaction medium for biocatalytic reactions with the enzyme AacSHC.
Department of Chemistry, Durham University, South Road, DH1 3LE Durham, UK; Institute of Physical Chemistry, University of Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart, Germany.
Anne K
AK
Steudle
Institute of Technical Biochemistry, University of Stuttgart, Allmandring 31,70569 Stuttgart, Germany.
Bettina M
BM
Nestl
Institute of Technical Biochemistry, University of Stuttgart, Allmandring 31,70569 Stuttgart, Germany.
Bernhard
B
Hauer
Institute of Physical Chemistry, University of Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart, Germany. Electronic address: cosima.stubenrauch@ipc.uni-stuttgart.de.
Cosima
C
Stubenrauch
D056450:Alicyclobacillus / Q000201:enzymology; D001711:Biotransformation; D002942:Circular Dichroism; D004655:Emulsions; D019751:Intramolecular Transferases / Q000378:metabolism*; D009795:Octanes / Q000737:chemistry
D004655:Emulsions; D009795:Octanes; D019751:Intramolecular Transferases; C066630:squalene-hopene cyclase; C026728:octane
Activity of squalene-hopene cyclase (AacSHC); Bicontinuous microemulsion; Biocatalysis in non-conventional media; Circular dichroism; Conformation of AacSHC in microemulsions