Research On Construction And Application Of The Dual Enzyme Systems

Enzymes are nature evolution of proteins with high specificity and strong catalyticability, which can catalyze certain chemistry reaction in mild conditions. Because ofthe unique supramolecular interaction between enzyme and its substrate, it becomes thefirst choice when studying the bionic system. Enzyme catalytic process is verycomplexity, but with the development of the genomics, proteomics, and computersimulation, people have a deeper understanding of the enzyme catalysis andapplication.Multi-enzyme synergistic catalytic system is one of the challenging researchtopics in the field of enzyme-catalyzed. Due to the complexity of the systems and theunstability property of the enzyme, limiting the development of the multi-enzymesynergistic catalysis system. However, the amazing ability of native enzymesdemonstrated the efficiency and specificity under mild conditions, still attractedscientists extensive attention. Therefore, the study of multi-enzyme synergisticcatalysis and its related application, has become a common concern in chemistry,biology and life sciences. Explore of multi-enzyme synergistic catalysis system hasgreat significance in understanding the evolution process of enzyme and therelationship between the tructure and function of enzyme. Herein, as guidance ofbionics, we used the dual-enzyme system for exploring antioxidant, self-healing andmicro motor.1. Construction of dual enzymatic antioxidant systemThe antioxidant enzymes, superoxide dismutase (SOD), catalase (CAT), andglutathione peroxidase (GPx) contribute dominatingly to enhance cellularantioxidative defense against oxidative stress in the human body. Thereinto, SOD is ametalloenzyme that catalyzes the dismutation of superoxide radical anion (O2-)toH2O2and dioxygen. H2O2is then detoxified either to H2O and O2by catalase (CAT)or to H2O by glutathione peroxidase (GPx). Studies indicated that each enzyme has aspecific as well as an irreplaceable function and they act in a cooperative or synergistic way to ensure a global cell protection, and only when an appropriatebalance between the activities of these enzymes is maintained, the optimal protectionof cells could be achieved.In recent years, there were considerable interests in preparing the enzyme mimicswith the properties of SOD or GPx for elucidating catalytic mechanism and forpotential pharmaceutical application. In order to further study the cooperation of theseenzymes in antioxidation and to generate efficient therapeutic agents, somebifunctional artificial enzymes with antioxidant enzyme activities have beenconstructed by chemical methods.Here, based on the understanding of the synergy of the natural antioxidant enzymes,we have carried out work as follow. Using computational design and geneticengineering methods, the main catalytic components of GPx were fabricated onto thesurface of ferritin. The resulting seleno-ferritin (Se-Fn) monomers can self-assembleinto nanocomposites which exhibit remarkable GPx activity due to the well organizedmulti-GPx catalytic centers. Subsequently, a porphyrin derivative was synthesized asSOD mimic to crosslink Se-Fn nanocomposites for the formation of a synergistic dualenzyme microgel, and this dual enzyme microgel has been proven to displaysignificantly better antioxidant ability than single GPx or SOD mimic in protectingcell from oxidative damage.2. Construction of dual enzymatic self-healing systemThe abilities to spontaneously heal injury and recover functionality are keyfeatures that increase the survivability and lifetime of the organism. In contrast,synthetic materials usually fail after damage or fracture. Inspired by nature, thedemand for self-healing materials is rapidly development because they can offer anew rote toward safer, longer-lasting products and lower production costs. Over thepast few decades, there were three kinds of conceptual self-healing systems have beenreported, such as capsule system, vascular system, and intrinsic system.As one of the acidity reversible covalent bonds, imine bond—from an amine andan aldehyde has been widely used in the construction of exotic molecules and extendstructures on account of the inherent ‘proof-reading’ and ‘error-checking’ associatedwith these reversible reactions. But more importantly, the equilibrium of imine bondformation between an imine and its corresponding precursor(s) can influenced by theexternal considerations, such as solvent, pH, and temperature.Herein, we reasoned that one such reaction, the glutaraldehyde by the reversible covalent attachment of the GOx and the bovine serum albumin (BSA) to the lysineresidue, could be well suited for the formation and functionalization of proteinhydrogels system. The BSA as a scaffolding sustain the hydrogels system and theGOx as a catalytic center play a key role to adjust the pH of the system by add extratraces of glucose. The glucose is oxidized to gluconolactone under the catalytic of theGOx, then gluconolactone hydrolyzed to gluconic acid to reduce the system pH. TheH2O2that generated by the catalytic reaction will be decomposition by the enzymecatalase (CAT) to avoid the glutaraldehyde is oxidized. With the change of the pH, theimine bonds provide us the opportunity to drive the reaction forward or backwards.3. Construction of dual enzymatic micro-motor systemLife is movement. For the nature forms, the material transport in cellular, DNAreplication, cell division and differentiation, muscle contraction, a series of importantlife activities are dependent on the movement of the biological molecular motors inthe cytoplasm. These motors are nanomachines which can be transform the energy ofbiochemistry to mechanical. In the natural world, the autonomous motion of biomotoris common. Protein motors and bacteria have formed a variety of sophisticated andperfect systems fuelled with chemical energy, and well-controlled nanomachines canexecute translational and rotational movement precisely. The outstanding performanceof these biomotors in nature has stimulated interest in synthesis of manmademicro-/nano-motors which can mimic the behaviors of biomotors to operate inlocally-supplied chemical fuels and achieve various functions. The first generation ofcatalytic motors on the micro-/nano-scale which exhibit autonomous self-propulsionin the presence of hydrogen peroxide makes this idea promising and exhibits potentialapplications in small cargo delivery and biosensing.Based on the catalytic decomposition of H2O2, we constructed a dual enzymemicro-motor system. The system applications the bubbles promote motor model.Motors that utilize this type of motion create bubbles on their catalytic side and theforce from the release of the bubbles causes the motion. This is a gradientlikemechanism since bubbles need to be generated on one side and not the other so thereis a change in bubble concentration with distance. We take silica gel as a carrier, anddecorate catalase (CAT) on the surface of silica. Then the silica gel was placed intothe system of glucose oxidase and glucose. Due to the glucose oxidase oxidation ofglucose, H2O2was generated. Catalase decomposition of H2O2release oxygen can bedriving silica sports. Due to the inhomogeneity of the silica surface, there are different sports ways in the system, such as linear motion and rotary motion. We anticipate thatthis system could provide a new approach for micro-and nano objects transport,bio-sensing and other areas in vivo application.