Synthetic Glycosidase Distinguishing Glycan and Glycosidic Linkage in Its Catalytic Hydrolysis

Hydrolytic nanozymes: Preparation, properties, and applications

Hydrolytic nanozymes, as promising alternatives to hydrolytic enzymes, can efficiently catalyze the hydrolysis reactions and overcome the operating window limitations of natural enzymes. Moreover, they exhibit several merits such as relatively low cost, easier recovery and reuse, improved operating stability, and adjustable catalytic properties. Consequently, they have found relevance in practical applications such as organic synthesis, chemical weapon degradation, and biosensing. In this review, we highlight recent works addressing the broad topic of the development of hydrolytic nanozymes. We review the preparation, properties, and applications of six types of hydrolytic nanozymes, including AuNP-based nanozymes, polymeric nanozymes, surfactant assemblies, peptide assemblies, metal and metal oxide nanoparticles, and MOFs. Last, we discuss the remaining challenges and future directions. This review will stimulate the development and application of hydrolytic nanozymes.

Molecularly imprinted materials for glycan recognition and processing

Carbohydrates are the most abundant organic molecules on Earth and glycosylation is the most common posttranslational modification of proteins. Glycans are involved in a plethora of biological processes including cell adhesion, bacterial and viral infection, inflammation, and cancer development. Coincidently, glycosides were some of the earliest molecules imprinted and have been instrumental in the development of covalent molecular imprinting technology. This perspective illustrates recently developed molecularly imprinted materials for glycan binding and processing. Novel imprinting techniques and postmodification led to development of synthetic glycan-binding materials capable of competing with natural lectins in affinity and artificial glycosidases for selective hydrolysis of complex glycans. These materials are expected to significantly advance glycochemistry, glycobiology, and related areas such as biomass conversion.

Rational design of allosteric switchable catalysts

Allosteric regulation, in many cases, involves switching the activities of natural enzymes, which further affects the enzymatic network and cell signaling in the living systems. The research on the construction of allosteric switchable catalysts has attracted broad interests, aiming to control the progress and asymmetry of catalytic reactions, expand the chemical biology toolbox, substitute unstable natural enzymes in the biological detection and biosensors, and fabricate the biomimetic cascade reactions. Thus, in this review, we summarize the recent outstanding works in switchable catalysts based on the allosterism of single molecules, supramolecular complexes, and self-assemblies. The concept of allosterism was extended from natural proteins to polymers, organic molecules, and supramolecular systems. In terms of the difference between these building scaffolds, a variety of design methods that tailor biological and synthetic molecules into controllable catalysts were introduced with emphasis.

Dynamic Tuning in Synthetic Glycosidase for Selective Hydrolysis of Alkyl and Aryl Glycosides

Enzymes use sophisticated conformational control to optimize the dynamics of their protein framework for efficient catalysis. Although it is difficult to employ a similar strategy to improve catalysis in a synthetic enzyme, we here report that modulation of the dynamics of the substrate in the active site is readily achievable in a complex between a molecularly imprinted nanoparticle and its acid cofactor, through tuning of the size and shape of the imprinted site. As the alkyl glucoside substrate is bound with increasing strength and held in a more tightly fitted pocket, the acid-catalyzed glycan hydrolysis becomes more difficult. A larger, wider active site, although less able to bind the substrate, affords a higher catalytic activity, likely due to easier alignment of the substrate and the acid cofactor for a general acid catalysis. The substrate selectivity is controlled by both the tightness of the aglycon-binding site and the orientation of the glycan-binding boroxole group.

Environmental Modulation of Chiral Prolinamide Catalysts for Stereodivergent Conjugate Addition

Synthetic chiral catalysts generally rely on proximal functional groups or ligands for chiral induction. Enzymes often employ environmental chirality to achieve stereoselectivity. Environmentally controlled catalysis has benefits such as size and shape selectivity but is underexplored by chemists. We here report molecularly imprinted nanoparticles (MINPs) that utilized their environmental chirality to either augment or reverse the intrinsic selectivity of a chiral prolinamide cofactor. The latter ability allowed the catalyst to produce products otherwise disfavored in the conjugate addition of aldehyde to nitroalkene. The catalysis occurred in water at room temperature and afforded γ-nitroaldehydes with excellent yields (up to 94%) and ee (>90% in most cases). Up to 25:1 syn/anti and 1:6 syn/anti ratios were achieved through a combination of catalyst-derived and environmentally enabled selectivity. The high enantioselectivity of the MINP also made it possible for racemic catalysts to perform asymmetric catalysis, with up to 80% ee for the conjugate addition.

Substrate Protection in Controlled Enzymatic Transformation of Peptides and Proteins

Proteins are involved in practically every single biological process. The many enzymes involved in their synthesis, cleavage, and posttranslational modification (PTM) carry out highly specific tasks with no usage of protecting groups. Yet, the chemists' strategy of protection/deprotection potentially can be highly useful, for example, when a specific biochemical reaction catalyzed by a broad-specificity enzyme needs to be inhibited, during infection of cells by enveloped viruses, in the invasion and spread of cancer cells, and upon mechanistic investigation of signal-transduction pathways. Doing so requires highly specific binding of peptide substrates in aqueous solution with biologically competitive affinities. Recent development of peptide-imprinted cross-linked micelles allows such protection and affords previously impossible ways of manipulating peptides and proteins in enzymatic transformations.

Molecular Imprinting: Green Perspectives and Strategies

Advances in revolutionary technologies pose new challenges for human life; in response to them, global responsibility is pushing modern technologies toward greener pathways. Molecular imprinting technology (MIT) is a multidisciplinary mimic technology simulating the specific binding principle of enzymes to substrates or antigens to antibodies; along with its rapid progress and wide applications, MIT faces the challenge of complying with green sustainable development requirements. With the identification of environmental risks associated with unsustainable MIT, a new aspect of MIT, termed green MIT, has emerged and developed. However, so far, no clear definition has been provided to appraise green MIT. Herein, the implementation process of green chemistry in MIT is demonstrated and a mnemonic device in the form of an acronym, GREENIFICATION, is proposed to present the green MIT principles. The entire greenificated imprinting process is surveyed, including element choice, polymerization implementation, energy input, imprinting strategies, waste treatment, and recovery, as well as the impacts of these processes on operator health and the environment. Moreover, assistance of upgraded instrumentation in deploying greener goals is considered. Finally, future perspectives are presented to provide a more complete picture of the greenificated MIT road map and to pave the way for further development.

Tandem Aldol Reaction from Acetal Mixtures by an Artificial Enzyme with Site-Isolated Acid and Base Functionalities

Site-isolation of catalysts can enable incompatible catalysts such as acid and base to be used in one pot for enhanced efficiency and other benefits. Although many synthetic platforms have been reported for this purpose, they generally do not possess the exquisite selectivity of site-isolated enzymes in nature. Here we report water-soluble protein-sized nanoparticles with site-isolated acids in the core and amines on the surface. The catalysts were made through molecular imprinting of cross-linked micelles, followed by facile one-step photoaffinity labeling of the imprinted binding site. With a tunable, substrate-specific active site, the bifunctional artificial enzyme catalyzed highly selective tandem cross aldol reaction between acetone and mixtures of isomeric aryl acetals. It could also transform a less reactive substrate over a more reactive one.

Selective Hydrolysis of Aryl Esters under Acidic and Neutral Conditions by a Synthetic Aspartic Protease Mimic

Aspartic proteases use a pair of carboxylic acids to activate water molecules for nucleophilic attack. Here we report a nanoparticle catalyst with a similar catalytic motif capable of generating a hydroxide ion in its active site even under acidic reaction conditions. The synthetic enzyme accelerated the hydrolysis of para-nitrophenyl acetate (PNPA) by 91,000 times and could also hydrolyze nonactivated aryl esters at pH 7. The distance between the two acids and, in particular, the flexibility of the catalytic groups in the active site controlled the catalytic efficiency. The synthetic enzyme readily detected the addition of a single methyl on the acyl group of the substrate, as well as the substitution pattern on the phenyl ring.