title: Activation volumes of enzymes adsorbed on silica particles.
abstract: The immobilization of enzymes on carrier particles is useful in many biotechnological processes. In this way, enzymes can be separated from the reaction solution by filtering and can be reused in several cycles. On the other hand, there is a series of examples of free enzymes in solution that can be activated by the application of pressure. Thus, a potential loss of enzymatic activity upon immobilization on carrier particles might be compensated by pressure. In this study, we have determined the activation volumes of two enzymes, α-chymotrypsin (α-CT) and horseradish peroxidase (HRP), when they are adsorbed on silica particles and free in solution. The experiments have been carried out using fluorescence assays under pressures up to 2000 bar. In all cases, activation volumes were found to depend on the applied pressure, suggesting different compressions of the enzyme-substrate complex and the transition state. The volume profiles of free and adsorbed HRP are similar. For α-CT, larger activation volumes are found in the adsorbed state. However, up to about 500 bar, the enzymatic reaction of α-CT, which is adsorbed on silica particles, is characterized by a negative activation volume. This observation suggests that application of pressure might indeed be useful to enhance the activity of enzymes on carrier particles.
authors.affiliation: Department of Chemistry and Chemical Biology, TU Dortmund University , D-44221 Dortmund, Germany.
authors.forename: Vitor
authors.initials: V
authors.lastname: Schuabb
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; D004795:Enzyme Stability; D004798:Enzymes; D004800:Enzymes, Immobilized / Q000737:chemistry* / Q000378:metabolism*; D006735:Horseradish Peroxidase / Q000737:chemistry* / Q000378:metabolism*; D008958:Models, Molecular; D011312:Pressure; D011487:Protein Conformation; D012822:Silicon Dioxide / Q000737:chemistry*
chemical_list: D004798:Enzymes; D004800:Enzymes, Immobilized; D012822:Silicon Dioxide; D006735:Horseradish Peroxidase; D002918:Chymotrypsin; C117608:alpha-chymotrypsin