title: Crowding enhances lipase turnover rate on surface-immobilized substrates.
abstract: Utilizing surface-immobilized synthetic lipid substrates containing the redox-active ferrocene groups, the enzymatic activity of lipase from Thermomyces lanuginosus was measured by the cyclic voltammetry method. The activity was correlated with the surface density of the protein by the ATR-IR spectroscopy and the total internal reflection ellipsometry. It was found that the lipase turnover rate significantly increases with its surface density. Despite expected hindrance effects due to the crowding of the enzyme molecules in the near surface-saturation range of concentrations, the turnover rate was consistently higher compared with the values measured at low concentrations. The effect was explained by the change in the surface arrangement of the enzyme. In the low concentration range, lipase adsorbs onto a surface adopting a predominantly horizontal position. At high concentrations, as the surface density approaches saturation, the enzyme molecules due to crowding are forced into the predominantly vertical position, which is more favorable for the activation of the lipase through the interaction between the "hydrophobic lid" of the lipase and the hydrophobic adsorbate surface.
authors.affiliation: State Research Institute Center for Physical and Technological Sciences, Savanoriu Avenue 231, LT-01108 Vilnius, Lithuania; Faculty of Electronics, Vilnius Gediminas Technical University, Sauletekio 11, LT-10223 Vilnius, Lithuania. Electronic address: zbalevicius@ar.fi.lt.
authors.forename: Zigmas
authors.initials: Z
authors.lastname: Balevicius
authors.affiliation: Institute of Biochemistry, Vilnius University, Vilnius LT-08662, Lithuania.
authors.forename: Dalia
authors.initials: D
authors.lastname: Ignatjeva
authors.affiliation: Institute of Biochemistry, Vilnius University, Vilnius LT-08662, Lithuania. Electronic address: gniaura@ktl.mii.lt.
authors.forename: Gediminas
authors.initials: G
authors.lastname: Niaura
authors.affiliation: State Research Institute Center for Physical and Technological Sciences, Savanoriu Avenue 231, LT-01108 Vilnius, Lithuania. Electronic address: iljaignatjev@yahoo.com.
authors.forename: Ilja
authors.initials: I
authors.lastname: Ignatjev
authors.affiliation: State Research Institute Center for Physical and Technological Sciences, Savanoriu Avenue 231, LT-01108 Vilnius, Lithuania. Electronic address: vikvai@ktl.mii.lt.
authors.forename: Viktoras
authors.initials: V
authors.lastname: Vaicikauskas
authors.affiliation: State Research Institute Center for Physical and Technological Sciences, Savanoriu Avenue 231, LT-01108 Vilnius, Lithuania. Electronic address: jgb@pfi.lt.
authors.forename: Gintautas Jurgis
authors.initials: GJ
authors.lastname: Babonas
authors.affiliation: Institute of Biochemistry, Vilnius University, Vilnius LT-08662, Lithuania. Electronic address: gintaras.valincius@bchi.vu.lt.
authors.forename: Gintaras
authors.initials: G
authors.lastname: Valincius
mesh_terms: D000327:Adsorption; D001203:Ascomycota / Q000201:enzymology*; D055162:Biocatalysis; D055664:Electrochemical Techniques; D004789:Enzyme Activation; D005656:Fungal Proteins / Q000737:chemistry / Q000378:metabolism*; D057927:Hydrophobic and Hydrophilic Interactions; D007700:Kinetics; D008049:Lipase / Q000737:chemistry / Q000378:metabolism*; D017550:Spectroscopy, Fourier Transform Infrared; D013379:Substrate Specificity; D013499:Surface Properties
chemical_list: D005656:Fungal Proteins; D008049:Lipase
keywords: Adsorption; Cyclic voltammetry; Electrochemistry; Lipase; Thermomyces lanuginosus; Turnover rate