Intrinsic, inherent, and observed kinetic data with immobilized enzymes: The concept of rotational masking

Determination of the intrinsic kinetic constants of immobilized glucose oxidase and catalase

Models of membrane systems containing immobilized glucose oxidase and catalase operating together or independently have been developed. A rotated disk electrode apparatus was employed with novel electrochemical operating conditions to experimentally determine mass transfer and intrinsic kinetic parameters of enzyme-containing membranes. The value of a mass transfer parameter that describes internal and external diffusion was first determined under conditions that do not permit the enzyme reactions. In a subsequent experiment with the reaction allowed, kinetic parameters corresponding to the intrinsic maximal velocity and Michaelis constants of the immobilized enzymes were estimated by regression analysis of data based on an appropriate two- or three- parameter model. It was found that immobilization reduced the maximal intrinsic velocity but had no detectable effect on the Michaelis constants. In all but one case- these methods for membrane characterization are nondestructive and can be used repeatedly on a given membrane. These techniques provide the means for quantitative comparisons of immobilization methods and make possible temporal studies of immobilized enzyme inactivation.

High-performance liquid chromatography of amino acids, peptides and proteins. CIII. Mass transfer resistances in ion-exchange and dye-affinity chromatography of proteins

Adsorption equilibria and rate kinetics have been investigated for the binding of several proteins, with different molecular geometries, to several ion-exchange and dye-affinity chromatographic resins with varying pore size and protein accessibilities. The pore geometry was shown to play a significant role in the protein capacity and loadability of both the ion-exchange and dye-affinity resins. For example the Fractogel HW75-Cibacron Blue F3GA affinity sorbent had the greatest capacity for the small protein, lysozyme, compared to the other Fractogel HW-Cibacron Blue F3GA sorbents, and similarly, the ion-exchange resins, such as DEAE-Fractogel 65, bound more human serum albumin (HSA), as opposed to the larger protein, ferritin. The apparent diffusion of protein from the bulk phase to the ligands/ionic sites was calculated to be considerably restricted when the pore to protein size ratio was small, as is the case of DEAE Fractogel 65/ferritin system, and the dye-affinity Fractogel HW55/HSA system. In these circumstances, pore diffusivity was calculated to be up to 100-fold smaller than bulk diffusivity.

High-performance liquid chromatography of amino acids, peptides and proteins. XCII Thermodynamic and kinetic investigations on rigid and soft affinity gels with varying particle and pore sizes

In these investigations Cibacron Blue F3GA was immobilized on soft gels, porous silicas, and non-porous glass beads. Hen egg white lysozyme, human serum albumin and yeast alcohol dehydrogenase were used as adsorbates with the dye-affinity sorbents. Batch experiments with continuous monitoring of protein concentration were employed to evaluate thermodynamic and kinetic behaviour of these proteins in finite bath systems. The observed adsorption kinetic rates of interaction of the above proteins with each of the dye-affinity sorbents were found to decrease with increasing protein molecular weight. Equilibration times, in the batch experimental mode, of the adsorption of lysozyme on the dye-affinity sorbents varied from 20 s for the non-porous glass beads with a size range of 20-40 microns to more than 60 min in the case of a porous sorbent with a particle diameter of 100-300 microns and 60 nm pore size. Furthermore, equilibration times, which represent the overall adsorption rates incorporating all the non-equilibrium effects, increased with all affinity systems when adsorption took place in the non-linear portion of the isotherm. The most dramatic increase was observed when sorbents with relatively high protein size to pore size ratios, lambda, were employed.