Effect of PbII on the Secondary Structure and Biological Activity of Trypsin

Corner Engineering: Tailoring Enzymes for Enhanced Resistance and Thermostability in Deep Eutectic Solvents

Deep eutectic solvents (DESs), heralded for their synthesis simplicity, economic viability, and reduced volatility and flammability, have found increasing application in biocatalysis. However, challenges persist due to a frequent diminution in enzyme activity and stability. Herein, we developed a general protein engineering strategy, termed corner engineering, to acquire DES-resistant and thermostable enzymes via precise tailoring of the transition region in enzyme structure. Employing Bacillus subtilis lipase A (BSLA) as a model, we delineated the engineering process, yielding five multi-DESs resistant variants with highly improved thermostability, such as K88E/N89 K exhibited up to a 10.0-fold catalytic efficiency (kcat /KM ) increase in 30 % (v/v) choline chloride (ChCl): acetamide and 4.1-fold in 95 % (v/v) ChCl: ethylene glycol accompanying 6.7-fold thermal resistance improvement than wild type at ≈50 °C. The generality of the optimized approach was validated by two extra industrial enzymes, endo-β-1,4-glucanase PvCel5A (used for biofuel production) and esterase Bs2Est (used for plastics degradation). The molecular investigations revealed that increased water molecules at substrate binding cleft and finetuned helix formation at the corner region are two dominant determinants governing elevated resistance and thermostability. This study, coupling corner engineering with obtained molecular insights, illuminates enzyme-DES interaction patterns and fosters the rational design of more DES-resistant and thermostable enzymes in biocatalysis and biotransformation.

Intestinal response of Rana chensinensis larvae exposed to Cr and Pb, alone and in combination

Although numerous investigations on the adverse impact of Cr and Pb have been performed, studies on intestinal homeostasis in amphibians are limited. Here, single and combined effects of Cr (104 μg/L) and Pb (50 μg/L) on morphological and histological features, bacterial community, digestive enzymes activities, as well as transcriptomic profile of intestines in Rana chensinensis tadpoles were assessed. Significant decrease in the relative intestine length (intestine length/snout-to-vent length, IL/SVL) was observed after exposure to Pb and Cr/Pb mixture. Intestinal histology and digestive enzymes activities were altered in metal treatment groups. In addition, treatment groups showed significantly increased bacterial richness and diversity. Tadpoles in treatment groups were observed to have differential gut bacterial composition from controls, especially for the abundance of phylum Proteobacteria, Firmicutes, Verrucomicrobia, Actinobacteria, and Fusobacteria as well as genus Citrobacter, Anaerotruncus, Akkermansia, and Alpinimonas. Moreover, transcriptomic analysis showed that the transcript expression profiles of GPx and SOD isoforms responded differently to Cr and/or Pb exposure. Besides, transcriptional activation of pro-apoptotic and glycolysis-related genes, such as Bax, Apaf 1, Caspase 3, PK, PGK, TPI, and GPI were detected in all treatment groups but downregulation of Bcl2 in Pb and Cr/Pb mixture groups. Collectively, these results suggested that Cr and Pb exposure at environmental relevant concentration, alone and in combination, could disrupt intestinal homeostasis of R. chensinensis tadpoles.

Protective effects of non-encapsulated and microencapsulated Lactobacillus delbrueckii subsp. bulgaricus in rainbow trout (Oncorhynchus mykiss) exposed to lead (Pb) via diet

The present study was designed to investigate the effects of dietary non-encapsulated and microencapsulated Lactobacillus delbrueckii subsp. bulgaricus on growth performance, intestinal enzymatic activities, antioxidant capacity and hepato-biochemical parameters of rainbow trout before or after exposure to lead via diet. Fingerling fish (16 ± 4 g) were divided into four groups: negative control (NC), positive control (PC), probiotic (PR) and encapsulated probiotic (EN-PR). During the pre-exposure period (days 0-45), fish in the NC and PC groups received the basal diet, whereas fish in the PR and EN-PR groups were fed with basal diet containing 108 CFU g−1 feed of non-encapsulated and microencapsulated probiotic, respectively. During the exposure period (days 46-66), the fish in the probiotic and PC groups were co-treated with 500 μg g−1 feed of lead nitrate. Blood, liver and gut samples were taken at days 0, 45, 52, 59 and 66. The results revealed that growth performance and intestinal enzymatic activities were significantly (p< 0.05) improved in the probiotic groups compared to the NC group (day 45). Dietary exposure to lead resulted in the highest levels of liver aspartate aminotransferase (AST), liver alkaline phosphatase (ALP) and serum malondialdehyde (MDA), and the lowest activities of serum superoxide dismutase (SOD) and catalase (CAT) in the PC group (day 66). The levels of liver ALP were significantly (p< 0.05) lower in the probiotic groups compared to the NC and PC groups prior to and after exposure to dietary lead. Serum levels of total protein, albumin, SOD, CAT and glutathione (GSH) were significantly increased in fish fed with both non-encapsulated and microencapsulated probiotics (p< 0.05). However, microencapsulated probiotic showed the greatest potential for alleviation of the disturbed activities of intestinal and hepatic enzymes, and improvement of serum biochemical and antioxidant parameters. Our findings suggest that L. delbrueckii subsp. bulgaricus, particularly in the microencapsulated form, can be used as a potential probiotic to protect rainbow trout from dietborne lead toxicity.

Intestinal response characteristic and potential microbial dysbiosis in digestive tract of Bufo gargarizans after exposure to cadmium and lead, alone or combined

The gastrointestinal tract is the largest immune organ in the body and meanwhile, accommodates a large number of microorganisms. Heavy metals could disturb the intestinal homeostasis and change the gut microbial composition. However, the information regarding the links between dysbiosis of gut microbiota and imbalance of host intestinal homeostasis induced by the mixture of heavy metals is insufficient. The present study investigates the effects of Cd/Pb, both single and combination exposure, on the growth performance, intestinal histology, digestive enzymes activity, oxidative stress and immune parameters, and intestinal microbiota in Bufo gargarizans tadpoles. Our results revealed that co-exposure of Cd-Pb induced more severe impacts not only on the host, but the intestinal microbiota. On the one hand, co-exposure of Cd-Pb significantly induced growth retardation, intestinal histological injury, decreased activities of digestive enzymes. On the other hand, Cd and Pb exposure, especially in mixed form, changed the diversity and richness, structure of microbiota. Also, the intestinal microbial composition was altered by Cd/Pb exposure (alone and combination) both at the different levels. Proteobacteria, act as front-line responder, was significantly increased in tadpoles under the exposure of metals. Finally, the functional prediction revealed that the disorders of metabolism and immune responses of intestinal microbiota was increased in tadpoles exposed to Cd/Pb (especially the mixture of Cd and Pb). Our research complements the understanding of links between changes in host fitness loss and intestinal microbiota and will add a new dimension of knowledge to the ecological risks of mixed heavy metals in amphibian.

Towards the identification of the gold binding region within trypsin stabilized nanoclusters using microwave synthesis routes

Elucidating the location of stabilized nanoclusters within their protein hosts is an existing challenge towards the optimized development of functional protein-nanoclusters. While nanoclusters of various metal compositions can be readily synthesized within a wide array of protein hosts and exhibit tailorable properties, the inability to identify the cluster stabilization region prevents controllable property manipulation of both metallic and protein components. Additionally, the ability to synthesize protein-nanoclusters in a consistent and high-throughput fashion is also highly desirable. In this effort, trypsin stabilized gold nanoclusters are synthesized through standard and microwave-enabled methodologies to determine the impact of processing parameters on the materials physical and functional properties. Density functional theory simulations are employed to localize high probability regions within the trypsin enzyme for Au25 cluster stabilization, which reveal that cluster location is likely within close proximity of the trypsin active region. Trypsin activity measurements support our findings from DFT, as trypsin enzymatic activity is eliminated following cluster growth and stabilization. Moreover, studies on the reactivity of Au NCs and synchrotron characterization measurements further reveal that clusters made by microwave-based techniques exhibit slight structural differences to those made via standard methodologies, indicating that microwave-based syntheses largely maintain the native structural attributes despite the faster synthetic conditions. Overall, this work illustrates the importance of understanding the connections between synthetic conditions, atomic-scale structure, and materials properties that can be potentially used to further tune the properties of metal cluster-protein materials for future applications.

PEG and mPEG-anthracene conjugate with trypsin and trypsin inhibitor: hydrophobic and hydrophilic contacts

The conjugation of trypsin (try) and trypsin inhibitor (tryi) with poly(ethylene glycol) (PEG) and methoxypoly(ethylene glycol) anthracene (mPEG-anthracene) was investigated in aqueous solution, using multiple spectroscopic methods, thermodynamic analysis, and molecular modeling. Thermodynamic parameters ΔS, ΔH, and ΔG showed protein-PEG bindings occur via H-bonding and van der Waals contacts with trypsin inhibitor forming more stable conjugate than trypsin. As polymer size increased more stable PEG-protein conjugate formed, while hydrophobic mPEG-anthracene forms less stable protein complexes. Modeling showed the presence of several H-bonding contacts between polymer and amino acids that stabilize protein-polymer conjugation. Polymer complexation induces more perturbations of trypsin inhibitor structure than trypsin with reduction of protein alpha-helix and major increase in random structures, indicating protein structural destabilization.

Conjugation of biogenic and synthetic polyamines with trypsin and trypsin inhibitor

Polyamine–protein conjugates can be used as delivery tools to transport antitumor polyamine analogues.

Molecular glues for manipulating enzymes: trypsin inhibition by benzamidine-conjugated molecular glues

Water-soluble bioadhesive polymers bearing multiple guanidinium ion (Gu+) pendants at their side-chain termini (Glue n -BA, n = 10 and 29) that were conjugated with benzamidine (BA) as a trypsin inhibitor were developed. The Glue n -BA molecules are supposed to adhere to oxyanionic regions of the trypsin surface, even in buffer, via a multivalent Gu+/oxyanion salt-bridge interaction, such that their BA group properly blocks the substrate-binding site. In fact, Glue10-BA and Glue29-BA exhibited 35- and 200-fold higher affinities for trypsin, respectively, than a BA derivative without the glue moiety (TEG-BA). Most importantly, Glue10-BA inhibited the protease activity of trypsin 13-fold more than TEG-BA. In sharp contrast, m Glue27-BA, which bears 27 Gu+ units along the main chain and has a 5-fold higher affinity than TEG-BA for trypsin, was inferior even to TEG-BA for trypsin inhibition.

Investigation of trypsin-CdSe quantum dot interactions via spectroscopic methods and effects on enzymatic activity

The paper presents the interactions between trypsin and water soluble cadmium selenide (CdSe) quantum dots investigated by spectrophotometric methods. CdSe quantum dots have strong ability to quench the intrinsic fluorescence of trypsin by a static quenching mechanism. The quenching has been studied at three different temperatures where the results revealed that electrostatic interactions exist between CdSe quantum dots and trypsin and are responsible to stabilize the complex. The Scatchard plot from quenching revealed 1 binding site for quantum dots by trypsin, the same has been confirmed by making isothermal titrations of quantum dots against trypsin. The distance between donor and acceptor for trypsin-CdSe quantum dot complexes is calculated to be 2.8 nm by energy transfer mechanisms. The intrinsic fluorescence of CdSe quantum dots has also been enhanced by the trypsin, and is linear for concentration of trypsin ranging 1-80 μl. All the observations evidence the formation of trypsin-CdSe quantum dot conjugates, where trypsin retains the enzymatic activity which in turn is temperature and pH dependent.

Effects of dietary Pb on accumulation, histopathology, and digestive enzyme activities in the digestive system of tilapia (Oreochromis niloticus)

With the increasing occurrence of dietary lead (Pb) contamination in aquatic environment, threat of the dietary Pb toxicity to aquatic organisms attracted more attention. In this study, after being exposed to dietary Pb at concentrations of 0, 100, 400, and 800-microg/g dry weight for 60 days, the groups of tilapia (Oreochromis niloticus) were sacrificed and sampled to analyze the effects of dietary Pb on accumulation, histopathology, and digestive enzyme activities in tissues of the digestive system. The results showed that the Pb accumulation in tissues increased with the dietary Pb concentrations. Moreover, Pb accumulated in sampled tissues in the following order: intestine > stomach > liver. By observation of liver histological sections in optical microscope, lesions could be detected in the Pb-contaminated groups. It was also demonstrated that the inhibitory effect of dietary Pb on digestive enzyme activities was dietary Pb concentration dependent. Different degrees of inhibition of enzyme activities were exhibited in sampled tissues. It was indicated that digestive enzyme activities in the digestive system might be considered as the potential biomarkers of dietary Pb contamination in tilapia.