Abstract: Disclosed is a hybrid enzyme containing a foreign peptide, the hybrid enzyme having an enzyme activity similar to that prior to the substitution or insertion of the peptide, and having a property that the hybrid enzyme activity is modulated or modified when a material having binding ability to the peptide introduced by substitution or insertion is bound to the peptide moiety. Using the hybrid enzyme, it becomes possible to assay a trace amount of CRP in a sample by a homogeneous colorimetry, and a macromolecule materials can be easily assayed in a homogeneous system.