Enhanced Activity of Immobilized or Chemically Modified Enzymes

Re-engineering enzymes with high activities in the given environments different from the physiological one has been constantly pursued for application of enzymatic catalysis in industrial biocatalytic processes, pharmaceutical industry, biosensing etc. Re-engineering enzyme catalysts by chemical approaches, including immobilization and chemical modification, represents a simple but effective route. The unusual phenomenon that immobilized or chemically modified enzymes display higher activities than native enzymes has been observed in both single- and multiple-enzyme systems. Recent achievements in enhancing enzymatic activities in both single-and multiple-enzyme systems by chemical approaches are summarized in this review. We propose that these enhanced enzymatic activities can be attributed to the well-designed specific interactions between immobilization carriers (or chemical modifiers) and enzymes, substrates, or reaction media. In addition to this mechanism, which is applicable for both single- and multiple-enzyme systems, other important factors responsible for enhanced activities of multiple-enzyme systems, including substrate channeling, kinetic matching, and an ordered spatial distribution of enzymes, are also discussed. Understanding the origin of enhanced activity in enzymatic catalysis may provide design efficient enzyme catalysts for practical applications.