Immobilization is designed to restrict the freedom of movement of an enzyme and, in doing so, places limitations on the enzyme and the biotransformation catalyzed by the enzyme (see Chapter 1 ). In practical terms, this often means that the normal procedures used for assay of the soluble enzyme activity, protein content, and so on, must be redesigned to accomodate the presence of the support material. In general, problems are likely to be experienced when the active agent in an assay procedure binds directly to the enzyme and measurement is based on the enzyme-reagent complex. Support materials are likely to cause interference in such procedures.