Evolving strategies for marine enzyme engineering:recent advances on the molecular modification of alginate lyase

Alginate,an acidic polysaccharide,is formed byβ-D-mannuronate(M)andα-L-guluronate(G).As a type of polysaccharide lyase,alginate lyase can efficiently degrade alginate into alginate oligosaccharides,having potential applications in the food,medicine,and agriculture fields.However,the application of alginate lyase has been limited due to its low catalytic efficiency and poor temperature stability.In recent years,various structural features of alginate lyase have been determined,resulting in modification strategies that can increase the applicability of alginate lyase,making it important to summarize and discuss the current evidence.In this review,we summarized the structural features and catalytic mechanisms of alginate lyase.Molecular modification strategies,such as rational design,directed evolution,conserved domain recombination,and non-catalytic domain truncation,are also described in detail.Lastly,the application of alginate lyase is discussed.This comprehensive summary can inform future applications of alginate lyases.

Molecular Modification of Benzophenone Derivatives for Lower Bioenrichment and Toxicity Through the Pharmacophore Model

In this study,we used the improved extreme-difference normalization method to calculate the comprehensive evaluation values of bioenrichment and toxicity of benzophenone UV light absor-bers(BPs).Based on this parameter,a 3D-QSAR(QSAR=quantitative structure activity relationship)pharmacophore model was constructed using Discovery Studio software and applied to the mole-cular modification of BPs.With three commonly used ingredients in sunscreen 2-hydroxy-4-methoxybenzophenone(BP-3),2,2'-dihydroxy-4,4'-dimethoxybenzophenone(BP-6)and 2,2'-dihydroxy-4-methoxybenzophenone(BP-8)as target molecules,we performed BPs substitution reaction based on the binding positions of characteristic elements of the pharmacophore model and designed BP derivatives with reduced bioenrichment and toxicity.Stability and function evaluation showed that while the stability of 6 BP derivatives was enhanced,the light absorption capacity was also significantly enhanced(from 9.16%to 43.16%).Molecular dynamics simulation results showed that the binding ability of BP-609 molecule with serum albumin was reduced by 16.37%compared with BP-6,and the binding with collagen could not occur spontaneously,which could be used as an explanation for the simultaneous reduction of its bioenrichment and toxicity.Besides,through the simulation of human metabolism,it was found that the liver metabolites of BP-609 were less toxic,which reduced the potential risk of human metabolism.It proved that the molecular modification scheme of BPs was environment-friendly.

Advances in molecular modification and efficient expression of key enzymes for functional saccharide preparation

Functional saccharide is a general term that is often used to refer to the functional oligosaccharides,functional saccharide alcohols,and functional dietary fibers.These functional saccharides exhibit some health benefiting effects,such as having low calorie,preventing dental caries,and regulating intestinal disorders.Functional saccharides are widely used in food,health products,and the healthcare fields.The preparation of functional saccharides is accomplished mainly through reactions involving transglycosylation,isomerization,or hydrolysis catalyzed by glycosyltransferases,saccharide isomerases,and glycohydrolases,respectively.However,the poor catalytic properties of natural enzymes and low fermentation yields have restricted the large-scale industrial production of functional saccharides.Therefore,molecular modification and efficient expression of key enzymes for functional-saccharide preparation are very important for promoting the low-cost large-scale production of functional saccharides.In this report,the recent advances in functional optimization and expression preparation of enzymes related to functional saccharides are reviewed.

Ultrathin origami accordion-like structure of vacancy-rich graphitized carbon nitride for enhancing CO_(2) photoreduction

Retaining the ultrathin structure of two-dimensional materials is very important for stabilizing their catalytic performances.However,aggregation and restacking are unavoidable,to some extent,due to the van der Waals interlayer interaction of two-dimensional materials.Here,we address this challenge by preparing an origami accordion structure of ultrathin twodimensional graphitized carbon nitride(oa-C_(3)N_(4))with rich vacancies.This novel structured oa-C_(3)N_(4) shows exceptional photocatalytic activity for the CO_(2) reduction reaction,which is 8.1 times that of the pristine C_(3)N_(4).The unique structure not only prevents restacking but also increases light harvesting and the density of vacancy defects,which leads to modification of the electronic structure,regulation of the CO_(2) adsorption energy,and a decrease in the energy barrier of the carbon dioxide to carboxylic acid intermediate reaction.This study provides a new avenue for the development of stable highperformance two-dimensional catalytic materials.

A novel insight of enhancing the hydrogen peroxide tolerance of unspecific peroxygenase from Daldinia caldariorum based on structure

Unspecific peroxygenases(UPOs, EC 1.11.2.1) is a kind of thioheme enzyme capable of catalyzing various oxidations of inert C–H bonds using H_(2)O_(2) as an oxygen donor without cofactors. However, the enhancement of the H_(2)O_(2) tolerance of UPOs is always challenging. In this study, the A161C mutant of r Dca UPO,which originates from Daldinia caldariorum, was found to be highly H_(2)O_(2)-resistant. Compared with the wild type, the mutant r Dca UPO-A161C showed a 10-h prolonged half-life and a 64% improved enzyme activity when incubated in 10 mmol/L H_(2)O_(2). The crystal structure analysis at 1.47 A showed that r Dca UPOA161C exhibited 10 α-helixes(cyan) and a series of ordered rings, forming a single asymmetric spherical structure. The two conserved domains near heme formed an active site with the catalytic PCP and EHD regions(Glu86, His87, Asp88 residues). The H_(2)O_(2) tolerance of r Dca UPO-A161C was preliminarily explored by comparing its structure with the wild type. Notably, r Dca UPO-A161C showed significantly higher catalytic efficiency than the wild type for the production of hydroxyl fatty acids. This study is anticipated to provide an insight into the structure-function relationship and expand potential applications of UPOs.

Engineering the thermostability of D-lyxose isomerase from Caldanaerobius polysaccharolyticus via multiple computer-aided rational design for efficient synthesis of D-mannose

D-Mannose is an attractive functional sugar that exhibits many physiological benefits on human health.The demand for low-calorie sugars and sweeteners in foods are increasingly available on the market.Some sugar isomerases,such as D-lyxose isomerase(D-LIase),can achieve an isomerization reaction between D-mannose and D-fructose.However,the weak thermostability of D-LIase limits its efficient conversion from D-fructose to D-mannose.Nonetheless,few studies are available that have investigated the molecular modification of D-LIase to improve its thermal stability.In this study,computer-aided tools including FireProt,PROSS,and Consensus Finder were employed to jointly design D-LIase mutants with improved thermostability for the first time.Finally,the obtained five-point mutant M5(N21G/E78P/V58Y/C119Y/K170P)showed high thermal stability and cat-alytic activity.The half-life of M5 at 65◦C was 10.22 fold,and the catalytic efficiency towards 600 g/L of D-fructose was 2.6 times to that of the wild type enzyme,respectively.Molecular dynamics simulation and intramolecular forces analysis revealed a thermostability mechanism of highly rigidity conformation,newly formed hydrogen bonds andπ-cation interaction between and within protein domains,and redistributed surface electrostatic charges for the mutant M5.This research provided a promising D-LIase mutant for the industrial production of D-mannose from D-fructose.

Recent Progress of Inorganic Hole-Transport Materials for Perovskite Solar Cells

Perovskite solar cells (PSCs) have achieved significant progress in the past decade and a certified power conversion efficiency (PCE) of 26.0% has been achieved.The widely used organic hole transport materials (HTMs) in PSCs are typically sensitive to the moisture environment and continuous light exposure.In contrast,the inorganic HTMs benefiting from their outstanding merits,such as excellent environmental stability,are considered as alternatives and have attracted much attention in PSCs.In this review,we provide a comprehensive summary of the fundamental properties and recent progress of inorganic HTMs in n-i-p and p-i-n structured PSCs.Additionally,we emphasize the importance of inorganic HTMs in the development of highly efficient and stable PSCs.

Insulation and Flame Retardancy Improvement of PBDEs Using 3D-QSAR Model Combined with a Fuzzy Membership Function Method

A three-dimensional quantitative structure-activity relationship(3D-QSAR)model based on the fuzzy membership function method was developed in this study,and then the model was applied to the molecular design of the enhanced comprehensive activities(insulation/flame retardancy)of polybrominated diphenyl ethers(PBDEs)considering their environmental behavior control,to develop environmental-friendly PBDE derivatives with outstanding functionality.Firstly,a fuzzy membership function method was employed to characterize the evaluation values of comprehensive activities of the functional properties of PBDEs based on the 3D-QSAR model.Secondly,a comprehensive activity 3D-QSAR model(CoMFA)of the functional properties of PBDEs was established,which demonstrated robustness and good predictive ability.Thirdly,a molecular modification scheme was designed to enhance the comprehensive activity of the functional properties of PBDEs considering the PBDE homologs BDE-138,BDE-183,and BDE-209 as target molecules.The resulting information indicated that the four PBDE derivatives with significantly enhanced functional properties,such as passing screening for toxicity,bioconcentration,migration,and biodegradability assessments with environmentally friendly results,were successfully designed(43.57%-82.14%enhancement).Finally,the mechanism analysis indicated that the enhanced functional properties of the modified PBDE derivatives were significantly related to the substitution positions and substitution groups of PBDEs.

Inhibition of thrombin by functionalized C_(60)nanoparticles revealed via in vitro assays and in silico studies

The studies on the human toxicity of nanoparticles（NPs） are far behind the rapid development of engineered functionalized NPs. Fullerene has been widely used as drug carrier skeleton due to its reported low risk. However, different from other kinds of NPs, fullerene-based NPs（C_（60） NPs） have been found to have an anticoagulation effect, although the potential target is still unknown. In the study, both experimental and computational methods were adopted to gain mechanistic insight into the modulation of thrombin activity by nine kinds of C_（60） NPs with diverse surface chemistry properties. In vitro enzyme activity assays showed that all tested surface-modified C_（60） NPs exhibited thrombin inhibition ability. Kinetic studies coupled with competitive testing using 3 known inhibitors indicated that six of the C_（60） NPs, of greater hydrophobicity and hydrogen bond（HB） donor acidity or acceptor basicity, acted as competitive inhibitors of thrombin by directly interacting with the active site of thrombin. A simple quantitative nanostructure-activity relationship model relating the surface substituent properties to the inhibition potential was then established for the six competitive inhibitors.Molecular docking analysis revealed that the intermolecular HB interactions were important for the specific binding of C_（60） NPs to the active site canyon, while the additional stability provided by the surface groups through van der Waals interaction also play a key role in the thrombin binding affinity of the NPs. Our results suggest that thrombin is a possible target of the surface-functionalized C_（60） NPs relevant to their anticoagulation effect.