Ceruloplasmin in flatland: the relationship between enzyme catalytic activity and surface hydrophilicity.

The effective immobilization of the enzyme on the substrate surface plays a key role especially in biocatalysis, medicine or industry. Herein, we showed the influence of substrate hydrophilicity on the activity of the physically immobilized ceruloplasmin. To control the hydrophilicity of the substrate, thiols with various terminal groups were used. We have found that the effectiveness of the catalytic process of multimeric protein is the highest in the situation of application of the highly hydrophilic substrate. In the case of physical adsorption, the orientation of the enzyme is random, however the application of the appropriate modifying layer enforces the desired enzyme orientation. The quartz crystal microbalance with dissipation (QCM-D) results showed that the crucial parameter for the highest and most durable catalytic activity of the enzyme is the orientation, not the amount of the physically adsorbed enzyme.