Enhanced Activity of Immobilized or Chemically Modified Enzymes

Abstract

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 new insights and inspiration to design efficient enzyme catalysts for practical applications.

A new generation approach in enzyme immobilization: Organic-inorganic hybrid nanoflowers with enhanced catalytic activity and stability

“…Recent developments have showed that enzymes have not been immobilized only on micro sized materials but also immobilized on various types and shapes of nano sized materials, such as nano spheres, fibers, tubes and pores. The support materials used in immobilization should have functional groups, insolubility in water, biocompatibility and a large surface area [2,8]. Although immobilizations make enzymes highly stable against environmental changes, reusable and economical, most of enzymes inevitably lose their catalytic activities after immobilization due to mass transfer limitations between the enzyme and substrate and unfavorable conformation [14,15].…”

“…The substrate specificity, low toxicity and the absence of production of undesirable products make enzymes have advantages over chemical catalysts in industrial applications [4]. Despite of these unique propeties of free enzymes, but easy degradation on their molecular structure at high temperatures, at acidic or 4 basic pHs and in the presence of organic solvents strictly limite their use [6,8]. They can not also be seperated and gained from the reaction medium to be re-used.…”

Co-immobilization of multiple enzymes by metal coordinated nucleotide hydrogel nanofibers: improved stability and an enzyme cascade for glucose detection

“…High enzyme stability is important for applications. 3 Deactivation of enzymes by high temperature and extreme pH are the major reasons for enzyme deactivation. The stability of the GOx&HRP@Zn/AMP nanofibers was examined in at different pH (from 7.4 to 10, Figure 5a) and temperature (from 25 to 90 C, Figure 5b) and compared to that of the free GOx and HRP in solution.…”

Formation of Functional Nanobiocatalysts with a Novel and Encouraging Immobilization Approach and Their Versatile Bioanalytical Applications

“…The water solubility and/or insolubility, biocompatibility, surface functionality and size and morphology are ciritcal features to choose the supports for immobilization. Using various external supports generally enabled us to arrange amount of immobilized enzymes and to reuse them [2,17]. Despite all these developments, most of immobilized enzymes have showed great stabilities towards environmental conditions (temprature, pH values etc.…”

“…While enzymes may react with one or a few substrates due to their substrate specificity, they may catalyze whole substrate or their certain parts [1][2][3]. However despite these advantages, short live time in aqueous and organic medium, quick loss of activity (at high temperatures, at acidic or basic pHs and high salt concentration), and lack of separation from reaction medium and reusability are potential disadvantages of free enzymes and which make them quite expensive and highly suppress their use in diverse range of applications [4][5][6][7].…”