The role of enzyme adsorption in the enzymatic degradation of an aliphatic polyester

Abstract

The enzyme catalyzed degradation of poly(3-hydroxybutyrate) (PHB) is a two-step process consisting of the adsorption of the enzyme on the surface of a PHB substrate and the cleavage of ester bonds. A deactivated enzyme was prepared by point mutagenesis to separate the two steps from each other. Measurements carried out with active and inactive enzymes on PHB particles proved that mutagenesis was successful and the modified enzyme did not catalyze degradation. Based on the Michaelis-Menten approach a kinetic model was proposed which could describe the processes quantitatively, the agreement between prediction and the measured data was excellent. The separation of the two processes allowed the determination of the adsorption kinetics of the enzyme; the rate constants of the adsorption and desorption process were determined for the first time. Comparison of these constants to reaction rates showed that adsorption is not instantaneous and can be the ratedetermining step. The area occupied by an enzyme molecule was also determined (13.1 nm 2) and it was found to be smaller than the value published in the literature (178 nm 2). The separation of the two steps makes possible the prediction and control of the degradation process.

Screening Enzymatic Degradation of Polyester Polyurethane with Fluorescent Single-walled Carbon Nanotube and Polymer Nanoparticle Conjugates

“…It is possible that the binding of enzymes on the sensor would contribute to the quenching in the fluorescence change (reaction ). The adsorption of proteins on nanoparticles is reported to occur in the time scale of minutes, , whose time scale is similar to the quenching in fluorescence observed in our experiments. However, we have compared the results of turbidity and fluorescence change (Figure b) and found that the turbidity change occurs immediately after enzyme addition.…”

Design of Immobilized Enzyme Biocatalysts: Drawbacks and Opportunities

“…[19][20][21][22][23] Many methods of immobilization are described and used in the literature to circumvent the possible instability problems of the enzymes as well as to optimize the various applications. In recent years, the empirical use of these immobilization techniques (for example, covalent bonding, 24 physical adsorption, 25 ionic adsorption, 26 crosslinking, 27 encapsulation, 28 etc) and their influences on the specificity, activity and stability of the enzymatic molecules, as well as the usability of the biocatalysts for application-related [29][30][31] reactions. 29,[32][33][34][35] These immobilized enzymes, bound to the solid supports, can simply be removed from the reaction mixture.…”

Progressing Plastics Circularity: A Review of Mechano-Biocatalytic Approaches for Waste Plastic (Re)valorization

“…A very important aspect of this family of enzymes is that they incorporate a substrate binding domain (SBD), which adsorbs on the polymer surface. Hence, hydrolysis by PHB-depolymerases is a two-step reaction, beginning with adsorption, which has its own kinetics and can be a rate-limiting step ( Polyák et al, 2019 ). It should be noted that the SBDs do not show exclusive affinity for the polymers the enzyme can actually hydrolyze ( Kasuya et al, 1996 ).…”