title: Effect of interfacial properties on the activation volume of adsorbed enzymes.
abstract: We have studied the enzymatic activities of α-chymotrypsin (α-CT) and horseradish peroxidase (HRP) that are adsorbed on various chemically modified planar surfaces under aqueous solution. The enzymes were adsorbed on bare quartz, hydrophobic poly(styrene) (PS), positively charged poly(allylamine hydrochloride) (PAH), and negatively charged poly(styrene sulfonate) (PSS). Activation volumes of the enzymes at the aqueous-solid interfaces were determined by using high-pressure total internal reflection fluorescence (TIRF) spectroscopy. Apparently, the pressure response of the adsorbed enzymes strongly depends on the interfacial properties. α-CT can be activated by pressure (increasing enzymatic rate) on negatively charged surfaces like quartz and PSS, whereas HRP is activated by pressure on hydrophobic PS. Corresponding negative activation volumes of -29 mL mol(-1) for α-CT on quartz, -23 mL mol(-1) for α-CT on PSS, and -35 mL mol(-1) for HRP on PS are found. In addition, the absolute activities of α-CT and HRP on quartz, PS, PAH and PSS were determined by UV absorption at ambient pressure. Remarkably, large activities are found on those surfaces that are associated with negative activation volumes. However, Fourier transform infrared (FTIR) spectra collected in attenuated total reflection (ATR) mode do not indicate major adsorption induced conformational changes of the enzymes at any interface studied. Overall, the results of this study show that the activity of immobilized enzymes can largely be enhanced by the right combination of adsorbent material and applied pressure.
authors.affiliation: TU Dortmund University, Department of Chemistry and Chemical Biology, D-44221 Dortmund, Germany.
authors.forename: Vitor
authors.initials: V
authors.lastname: Schuabb
authors.affiliation: TU Dortmund University, Department of Chemistry and Chemical Biology, D-44221 Dortmund, Germany.
authors.forename: Süleyman
authors.initials: S
authors.lastname: Cinar
authors.affiliation: TU Dortmund University, Department of Chemistry and Chemical Biology, D-44221 Dortmund, Germany. Electronic address: claus.czeslik@uni-dortmund.de.
authors.forename: Claus
authors.initials: C
authors.lastname: Czeslik
mesh_terms: D000327:Adsorption; D000818:Animals; D002417:Cattle; D002918:Chymotrypsin / Q000737:chemistry* / Q000378:metabolism; D004789:Enzyme Activation; D004800:Enzymes, Immobilized / Q000737:chemistry* / Q000378:metabolism; D006735:Horseradish Peroxidase / Q000737:chemistry / Q000378:metabolism; D057927:Hydrophobic and Hydrophilic Interactions; D010179:Pancreas / Q000201:enzymology; D011073:Polyamines / Q000737:chemistry*; D011137:Polystyrenes / Q000737:chemistry*; D011312:Pressure; D011791:Quartz; D017550:Spectroscopy, Fourier Transform Infrared; D013499:Surface Properties
chemical_list: D004800:Enzymes, Immobilized; D011073:Polyamines; D011137:Polystyrenes; D011791:Quartz; C063994:polyallylamine; C003321:polystyrene sulfonic acid; D006735:Horseradish Peroxidase; D002918:Chymotrypsin; C117608:alpha-chymotrypsin
keywords: Adsorption; Enzyme; Fluorescence spectroscopy; Infrared spectroscopy; Pressure