title: Conformation and activity of lipase B from Candida antarctica in bicontinuous microemulsions.
abstract: The paper at hand deals with the influence of the pH-value on the conformation and activity of the lipase B from Candida antarctica (CalB) which is incorporated in a bicontinuous microemulsion. The microemulsion used for this purpose consists of water/NaCl, n-octane, and the non-ionic surfactant penthaethylene glycol monodecylether (C10E5). The conformational study clearly shows (1) that CalB molecules are partitioned between the interfacial monolayer and the water domains and (2) that the pH-value of the microemulsion's water domains strongly influences the conformation of CalB at the interfacial monolayer. From these observations we conclude that there is a continuous exchange between the CalB molecules, which are located at the interfacial monolayer and those which are located in the water domains of the microemulsion. This exchange strongly influences the CalB conformation in both regions. In addition to the conformation, we also studied the catalytic activity of CalB. The catalytic measurements revealed a bell-shaped dependence between the CalB activity and the pH-value. The maximum catalytic activity of CalB in bicontinuous microemulsions was observed at pH=5.5. At this pH we observed the highest amount of α-helix conformation of the CalB molecules that are located at the interfacial monolayer, which, in turn, allows connecting the activity with the conformation.
authors.affiliation: Institute of Physical Chemistry, University of Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart, Germany.
authors.forename: Mireia
authors.initials: M
authors.lastname: Subinya
authors.affiliation: Department of Chemistry, Durham University, South Road, DH1 3LE, UK.
authors.forename: Anne K
authors.initials: AK
authors.lastname: Steudle
authors.affiliation: Institute of Biochemistry, University of Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart, Germany.
authors.forename: Tomasz P
authors.initials: TP
authors.lastname: Jurkowski
authors.affiliation: Institute of Physical Chemistry, University of Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart, Germany. Electronic address: cosima.stubenrauch@ipc.uni-stuttgart.de.
authors.forename: Cosima
authors.initials: C
authors.lastname: Stubenrauch
mesh_terms: D055162:Biocatalysis; D002175:Candida / Q000201:enzymology*; D002942:Circular Dichroism; D004655:Emulsions / Q000737:chemistry*; D005656:Fungal Proteins / Q000737:chemistry / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008049:Lipase / Q000737:chemistry / Q000378:metabolism*; D008956:Models, Chemical; D015394:Molecular Structure; D009596:Nitrophenols / Q000737:chemistry / Q000378:metabolism; D009795:Octanes / Q000737:chemistry; D010168:Palmitates / Q000737:chemistry / Q000378:metabolism; D019308:Palmitic Acid / Q000737:chemistry / Q000378:metabolism; D011487:Protein Conformation; D012965:Sodium Chloride / Q000737:chemistry; D013499:Surface Properties; D013501:Surface-Active Agents / Q000737:chemistry; D014867:Water / Q000737:chemistry
chemical_list: D004655:Emulsions; D005656:Fungal Proteins; D009596:Nitrophenols; D009795:Octanes; D010168:Palmitates; D013501:Surface-Active Agents; D014867:Water; C050015:4-nitrophenyl palmitate; D019308:Palmitic Acid; D012965:Sodium Chloride; D008049:Lipase; C026728:octane; C024836:4-nitrophenol
keywords: Bell-shaped pH-dependent activity; Enzyme conformation in bulk and at interface; Lipase B from Candida antarctica (CalB) in bicontinuous microemulsions