Protein adsorption and leakage in carrier–enzyme systems

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Abstract
The capability of binding enzymes adsorptively to unmodified and silanized silica and glass as well as modified polystyrene carriers was studied for α-amylase, β-amylase, and α-chymotrypsin. In most cases a high percentage of protein was bound very firmly under considerable loss of activity. The leakage of protein from the carriers was studied by measuring the intrinsic protein fluorescence on β-amylase adsorptively bound to aminopropyl silica, aminomethyl, and hexadecylaminomethyl polystyrene. It was compared with the leakage of β-amylase covalently bound to the same carriers via glutaraldehyde, trichloro-triazine, or benzoquinone. In the absence and in the presence of substrate, at 25 and at 60°C, the leakage rates of the adsorptively bound enzymes were not higher than in the covalently bound systems. The poorest binding stability was found in benzoquinone-coupled β-amylase derivatives. It is even reduced at higher temperatures, whereas the temperature did not show any remarkable influence on the leakage of the other derivatives. In adsorptively as well as in all the covalently bound systems, the presence of substrate did not promote the protein leakage.