Because most enzymes are a kind of protein, proteins are highly specific (the spatial structure of proteins is diverse, and one spatial structure corresponds to one characteristic).
Enzyme-protein/peptide conjugates, or cross-linked enzymes, are constructed for different applications. A typical example is the conjugation of “activated” horseradish peroxidase (HRP) to target antibody, protein, or peptide in immunoassays. On the other hand, cross-linking of enzyme molecules, as carrier-free immobilization technology, can expand industrial enzyme arsenal by increasing stability during use and storage. The conjugation reaction with proteins or peptides is usually via small molecular linkers (e.g. Glutaraldehyde) or enzymes (e.g. Transglutaminase), also known as cross-linking procedures.
