structure and its activity. This paper is an attempt to a better A proteolytic enzyme, a-chymotrypsin, and a lipolytic enzyme, understanding of the properties of a proteolytic enzyme (acutinase, were adsorbed from aqueous solution onto a hydrophobic chymotrypsin) and a lipolytic enzyme (cutinase) when they Teflon surface and a hydrophilic silica surface. We investigated are immobilized on a solid support.
the influence of adsorption on the structure, the structure thermal Nowadays, various ways of immobilizing enzymes are stability and the activity of these enzymes. Probing the protein well-known. The ones most commonly used are entrapment structure by circular dichroism spectroscopy indicates that Teflon (i.e., in gels, semipermeable membranes, or vesicles), adpromotes the formation of helical structure in a-chymotrypsin, sorption (via e.g., hydrophobic and ionic interactions), and but the reverse effect is found with cutinase. The perturbed protein covalent binding (i.e., formation of a covalent bond between structures on Teflon are remarkably stable, showing no heat-induced structural transitions up to 100ΠC, as monitored by differen-the enzyme and the support material via an activating agent tial scanning calorimetry. Contact with the hydrophilic silica sursuch as glutaraldehyde). Among them, immobilization by face leads to a loss in the helix content of both proteins. Differential physical adsorption is the simplest method and is certainly scanning calorimetry points to a heterogeneous population of adthe method which offers the mildest experimental conditions sorbed protein molecules with respect to their conformational for obtaining an enzyme-particle complex. We used physistates. The fraction of the native-like conformation in the adsorbed cal adsorption to bind a-chymotrypsin and cutinase molelayer increases with increasing coverage of the silica surface by cules to the various support materials. the proteins. The specific enzymatic activity in the adsorbed state Because of the types of forces involved in the physical qualitatively correlates with the fraction of proteins in the nativeadsorption of enzymes onto solids, parameters such as pH, like conformation. α§ 1997 Academic Press ionic strength, and temperature must be controlled. Likewise,