Upon interaction with a hydrophobic latex surface, enzymes at low solution concentrations have been demonstrated to lose their catalytic activity. It is proposed that this loss is due to a structural change of the protein when the hydrophobic interior of the enzyme exposes itself to the hydrophobic surface, thus "spreading" the macromolecule at the solid-liquid interface. All enzymes investigated (alkaline phosphatase, β-galactosidase, lysozyme, horseradish peroxidase, catalase, and glucose 6-phosphate dehydrogenase) exhibited this inactivation phenomenon upon contact with a 0.099-μm, weakly negatively charged polystyrene latex. The isotherms generated from the inactivation data are non-Langmuirian and suggest that a change in the type of association between the protein and the surface occurs when moving toward higher solution concentrations. The kinetics of the inactivation process and the effects of solution conditions (pH, ionic strength) are also reported. © 1987.
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