Amino Acid Binding Research Articles

Revealing Allosteric Mechanism of Amino Acid Binding Proteins from Open to Closed State.

Amino acid binding proteins (AABPs) undergo significant conformational closure in the periplasmic space of Gram-negative bacteria, tightly binding specific amino acid substrates and then initiating transmembrane transport of nutrients. Nevertheless, the possible closure mechanisms after substrate binding, especially long-range signaling, remain unknown. Taking three typical AABPs-glutamine binding protein (GlnBP), histidine binding protein (HisJ) and lysine/arginine/ornithine binding protein (LAOBP) in Escherichia coli (E. coli)-as research subjects, a series of theoretical studies including sequence alignment, Gaussian network model (GNM), anisotropic network model (ANM), conventional molecular dynamics (cMD) and neural relational inference molecular dynamics (NRI-MD) simulations were carried out. Sequence alignment showed that GlnBP, HisJ and LAOBP have high structural similarity. According to the results of the GNM and ANM, AABPs' Index Finger and Thumb domains exhibit closed motion tendencies that contribute to substrate capture and stable binding. Based on cMD trajectories, the Index Finger domain, especially the I-Loop region, exhibits high molecular flexibility, with residues 11 and 117 both being potentially key residues for receptor-ligand recognition and initiation of receptor allostery. Finally, the signaling pathway of AABPs' conformational closure was revealed by NRI-MD training and trajectory reconstruction. This work not only provides a complete picture of AABPs' recognition mechanism and possible conformational closure, but also aids subsequent structure-based design of small-molecule oncology drugs.

Alanine Scanning of the Unstructured Region of Ara h 2 and of a Related Mimotope Reveals Critical Amino Acids for IgE Binding.

The unstructured region of Ara h 2, referred to as epitope 3, contains a repeated motif, DYPSh (h = hydroxyproline) that is important for IgE binding. IgE binding assays to 20mer and shorter peptides of epitope 3, defines a 16mer core sequence containing one copy of the DPYSh motif, DEDSYERDPYShSQDP. Thisstudy performs alanine scanning of this and a related 12mer mimotope, LLDPYAhRAWTK. IgE binding, using a pool of 10 sera and with individual sera, is greatly reduced when alanine is substituted for aspartate at position 8 (D8; p < 0.01), tyrosine at position 10 (Y10; p < 0.01), and hydroxyproline at position 12 (h12; p < 0.001). IgE binding to alanine-substituted peptides of a mimotope containing the DPY_h motif confirm the critical importance of Y (p < 0.01) and h (p < 0.01), but not D. Molecular modeling of the core and mimotope suggests an h-dependent conformational basis for the recognition of these sequences by polyclonal IgE. IgE from pooled sera and individual sera differentially bound amino acids throughout the sequences of Epitope 3 and its mimotope, with Y10 and h12 being most important for all sera. These results are highly significant for designing hypoallergenic forms of Ara h 2.

Drug Repurposing of Clinically Approved Drugs to Target Epithelial-mesenchymal Transition Using Molecular Docking Approach

Introduction: Epithelial-mesenchymal transition (EMT) is a process of epithelial transformation into mesenchymal cells. It is also a process that contributes to the progression of fibrosis and cancer metastasis. Transforming growth factor-beta (TGF-β), as a potent inducer of EMT, has therefore became a potential therapeutic target. However, clinical developments of TGF-β inhibitors have been un-successful due to safety risks. Hence, drug repurposing of existing safe-to-use drugs could over-come this issue. Methods: In this study, the TGF-β receptor type 1 (ALK5) was selected as the target protein. Molecular docking was performed using known ALK5 inhibitors as positive controls. Clinical drugs with similar binding affinity and amino acid interaction were selected for in vitro experimental validation. Results: ALK5 inhibitor demonstrated binding affinities ranging from -11.2 to -9.5 kcal/mol. Analysis of amino acid interaction revealed that Val219, Ala230, Lys232, and Leu340 amino acid residues are crucial for binding. Subsequent screening of clinically approved drugs against ALK5 showed top five potential drugs (ergotamine, telmisartan, saquinavir, indinavir, and nelfinavir). The selected drugs were tested in TGF-β1-induced normal human bronchial epithelial cell line, BEAS-2B. Western blot analysis showed that the drugs did not exhibit inhibitory effects on the downregulation of epithelial proteins (E-cadherin) and upregulation of mesenchymal proteins (vimentin and α-smooth muscle actin). Conclusion: Based on these experimental outcome, it is postulated that the results from molecular docking were false positives. The tested drugs in this study could serve as negative controls in future screening against ALK5 protein.

STRUCTURAL PREDICTION OF HUMAN ZIP 2 AND ZIP4 BASED ON HOMOLOGY MODELLING AND MOLECULAR SIMULATION

Objective: This study aimed to analyze the structural proteins of zinc transporters as the target for drug actions and their molecular interactions. Methods: The present study is about the homology modelling and analysis of the zinc transporter function using the in silico molecular modelling method. Homology modelling predicts the 3D structure of a protein based on the sequence alignment with one or more template proteins of known structure. This study using in silico molecular modelling method, explains the 3D structure of human ZIP 2 and ZIP4 with Ramachandran Plot analysis, physical and chemical characteristics, transmembrane prediction with structural biology, and binding site prediction through molecular docking simulation. Results: Based on the physicochemical properties of the 3D structure of the ZIP2 and ZIP4 proteins, each comprises 309 amino acids and 582 amino acids with pI values of 5.85 and 5.24. The amino acid composition analysis showed that both proteins contain many Leucine amino acids. The Ramachandran diagram concludes that both proteins are stable in the stereochemical conformation forming a secondary structure. The binding amino acids on ZIP2 include Glu281, His216, Ser284, and Arg46. The binding amino acids in ZIP4 include Gln148, Gln154, Thr155, His197, Ala138, and Lys157. Conclusion: Establishment of the structure and function of human ZIP2 and ZIP4 as zinc transporters in cell membranes and prediction of ZIP2 and ZIP4 binding sites through molecular dcoking.

Reparative and Antioxidant Effects of New Analogues of Immunomodulator Thymogen in Experimental Model of Liver Damage.

We studied the reparative and antioxidant effects of Thymogen and its new structural analogues obtained by binding amino acid D-Ala to the N- or C-end of the peptide molecule in acute toxic hepatopathy. Intragastric administration of carbon tetrachloride for 5 days caused the development of fat degeneration of hepatocytes, a decrease in catalase activity, and an increase in malondialdehyde concentration. Administration of peptides suppressed oxidative peroxidation and stimulated reparative regeneration of hepatocytes; Thymogen analogues produced more pronounced hepatotropic and antioxidant effects than Thymogen. Inclusion of D-Ala enhanced the effect of Thymogen on the processes of regeneration in hepatocytes and the antioxidant effect under conditions of acute carbon tetrachloride hepatopathy. The highest efficiency was achieved when the amino acid was added to the C-end of the molecule.

Mycobacterium tuberculosis Rv2324 is a multifunctional feast/famine regulatory protein involved in growth, DNA replication and damage control

Feast/famine regulatory proteins (FFRPs) are multifunctional regulators. We show that Mtb Rv2324 is important for growth, survival, and countering DNA damage in Mycobacterium tuberculosis (Mtb). DNA-relaxation activity against linear and supercoiled substrates suggest its involvement in transcription activation, while its high affinity for recombination, replication and repair substrates suggest a role there too. Small-Angle-X-ray scattering supports the adoption of an ‘open’ quaternary association in response to amino-acid binding. Size-exclusion-chromatography and glutaraldehyde cross-linking identify the adoption of diverse oligomers modulated by amino-acid binding, and DNA interactions. We tested G52A, G101T and D104A mutants which correspond to highly conserved residues, distal to the DNA-binding site, and are important for amino acids binding. G101T exhibits increased DNA affinity, while G52A and D104A exhibit weak DNA-binding thereby suggesting that they mediate effector-binding, and DNA binding activities. Gain and loss-of-function studies show that Rv2324 overexpression promotes growth-rate, while its knock-down leads to retarded growth. Rv2324 down-regulation lowers Mtb survival inside resting and IFN-ϒ-activated macrophages. Rv2324 protects the pathogen from DNA damage, as evidenced by the reduction in the knockdown strain's survival following treatment with H2O2 and UV light. Overall, we show that Rv2324 plays a crucial role in regulating survival and growth of Mtb.

SLC12A Cryo-EM: Analysis of relevant ion binding sites, structural domains and amino acids.

The SLC12A superfamily of membrane transporters modulate the movement of cations coupled with chloride across the membrane. In doing so, these cotransporters are involved in numerous aspects of human physiology: cell volume regulation, ion homeostasis, blood pressure regulation, and neurological action potential via intracellular chloride concentration modulation. Their physiological characterization has been largely studied; however, understanding the mechanics of their function and relevance of structural domains or specific amino acids has been a pending task. In recent years, single-particle cryogenic electron microscopy (cryo-EM), has been successfully applied to members of the SLC12A family including all KCCs, NKCC1 and recently NCC; revealing structural elements that play key roles in their function. The present review analyzes the data provided by these cryo-EM reports focusing on structural domains and specific amino acids involved in ion binding, domain interactions, and other important SCL12A structural elements. Comparison of cryo-EM data from NKCC1 and KCCs is presented in the light of the two recent NCC cryo-EM studies, to propose insight into structural elements that might also be found in NCC and are necessary for its proper function. On the final sections, the importance of key coordination residues for substrate specificity and their implication on various pathophysiological conditions and genetic disorders is reviewed, as this could provide the basis to correlate structural elements with the development of novel and selective treatments, as well as mechanistic insight into the function and regulation of CCCs.

Beyond Stereoisomeric Effects: Exploring the Importance of Intermolecular Electron Spin Interactions in Biorecognition.

This work shows that electron spin polarization and stereoisomeric effects make comparable contributions to the enantioselective binding of amino acids. Magneto-electrochemical quartz crystal microbalance methods are used to study the adsorption of chiral amino acids onto a monolayer film of chiral molecules that are spin polarized by an underlying ferromagnetic substrate. The direction of the electron spin polarization affects both the kinetics and thermodynamics of the enantiospecific adsorption of the amino acids. Comparison of these data with the circular dichroism (CD) spectra of the amino acid adsorbates shows that the CD spectrum of the interacting group provides a good figure-of-merit for predicting the contributions of electron spin to the intermolecular interaction. These findings demonstrate the importance of electron spin in enantioselective intermolecular interactions between chiral amino acids and represent a paradigm shift for how selectivity should be viewed in biorecognition.

Antiviral Potential of Antillogorgia americana and elisabethae Natural Products against nsp16–nsp10 Complex, nsp13, and nsp14 Proteins of SARS-CoV-2: An In Silico Investigation

Biomolecules of marine origin have many applications in the field of biotechnology and medicine, but still hold great potential as bioactive substances against different diseases. The purification or total synthesis of marine metabolites is expensive, and requires a reliable selection method to reveal their pharmaceutical potential prior to clinical validation. This study aimed to explore the hidden potential of natural products from the gorgonian genus Antillogorgia as anti-SARS-CoV-2 agents, via binding affinity assessments and molecular dynamics (MDs) simulations. The three-dimensional protein structures of the nsp16–nsp10 complex, nsp13, and nsp14 were acquired from the RCSB PDB database. All 165 natural products (NPs) were discovered using the PubChem, ChemSpider, and CMNPD databases. The freeware Autodock Vina was used to conduct the molecular docking procedure, once the proteins and ligands were prepared using BIOVIA discovery studio and Avogadro software v1.95. Before running MDs simulations using the CABS-flex 2.0 website, the binding affinity assessments and amino acid interactions were carefully examined. Just twelve NPs were selected, and five of those NPs interacted optimally with the catalytic amino acids of proteins. To conclude, pseudopterosin A (−8.0 kcal/mol), seco-pseudopterosin A (−7.2 kcal/mol), sandresolide B (−6.2 kcal/mol), elisabatin A (−7.0 kcal/mol), and elisapterosin A (−10.7 kcal/mol) appeared to be the most promising candidates against the nsp16–nsp10, nsp13, and nsp14 proteins.

Investigating the Roles of Active Site Residues in Mycobacterium tuberculosis Indole-3-glycerol Phosphate Synthase, a Potential Target for Antitubercular Agents.

Mycobacterium tuberculosis drug resistance is emerging and new drug targets are needed. Tryptophan biosynthesis is necessary for M. tuberculosis replication and virulence. Indole-3-glycerol phosphate synthase (IGPS) catalyzes a step in M. tuberculosis tryptophan biosynthesis and has been suggested as a potential anti-infective target, but our understanding of this enzyme is limited. To aid in inhibitor design and gain a greater mechanistic picture of this enzyme, there is a need to understand the roles of active site amino acids in ligand binding and catalysis. In this work, we explored the roles of conserved active site amino acids Glu57, Lys59, Lys119, Glu168, and Glu219. Mutation of each to Ala results in loss of all detectable activity. The Glu57Gln, Lys59Arg, Lys119Arg, Glu168Gln, and Glu219Asp mutations result in large activity losses, while Glu219Gln has enhanced activity. Analysis of the enzymatic data yields the following main conclusions: (A) Lys119 is the likely catalytic acid in the CdRP ring closure step. (B) Glu168 stabilizes a charged reaction intermediate and may also be the catalytic base. (C) Glu57, Glu219, and Lys119 form a closely arranged triad in which Glu57 and Glu219 modulate the pKa of Lys119, and thus overall activity. This increased understanding of inter- and intramolecular interactions and demonstration of the highly coordinated nature of the M. tuberculosis IGPS active site provide new mechanistic information and guidance for future work with this potential new drug target.

Exploration of selected monoterpenes as potential TRPC channel family modulator in lung cancer, an in-silico upshot

Lung cancer is still the most frequent cause of cancer-related death, accounting for nearly two million cases yearly. As cancer is a multifactorial disease, developing novel molecular therapeutics that can simultaneously target multiple associated cellular processes has become necessary. Ion channels are diverse regulators of cancer-related processes such as abnormal proliferation, invasion, migration, tumor progression, inhibition of apoptosis, and chemoresistance. Among the various families of ion channels, the transient receptor potential canonical channel family steps out in the context of lung cancer, as several members have been postulated as prognostic markers for lung cancer. Phytochemicals have been found to have health benefits in the treatment of a variety of diseases and disorders. Among phytochemicals, monoterpenes are effective in treating both the early and late stages of cancer. The molecular docking interaction analysis was conducted to evaluate the binding potential of selected monoterpenes with TRPC3, TRPC4, TRPC5, and TRPC6 involved in different phases of carcinogenesis. Amongst the selected monoterpenes, thymoquinone exhibited the highest binding energy of −6.7 kcal/mol against the TRPC4 channel, and all amino acid binding residues were similar to those of the known inhibitor for TRPC4. In addition, molecular-dynamic simulation results parameters, such as RMSD, RMSF, and Rg, indicated that thymoquinone did not impact the protein compactness and exhibited stability during the interaction. The average interaction energy between thymoquinone and TRPC4 protein was −26.85 kJ/mol. In-silico Drug-likeness and ADMET profiling indicated that thymoquinone is a druggable candidate with minimal toxicity. We propose further investigation and evaluation of thymoquinone for lead optimization and drug development. Communicated by Ramaswamy H. Sarma

Mapping Peptide-Protein Interactions by Amine-Reactive Cleavable Photoaffinity Reagents.

Photoaffinity labeling followed by tandem mass spectrometry is an often used strategy to identify protein targets of small-molecule drugs or drug candidates, which, under ideal conditions, enables the identification of the actual drug binding site. In the case of bioactive peptides, however, identifying the distinct binding site is hampered because of complex fragmentation patterns during tandem mass spectrometry. We here report the development and use of small cleavable photoaffinity reagents that allow functionalization of bioactive peptides for light-induced covalent binding to their protein targets. Upon cleavage of the covalently linked peptide drug, a chemical remnant of a defined mass remains on the bound amino acid, which is then used to unambiguously identify the drug binding site. Applying our approach to known peptide-drug/protein pairs with reported crystal structures, such as the calmodulin-melittin interaction, we were able to validate the identified binding sites based on structural models. Overall, our cleavable photoaffinity labeling strategy represents a powerful tool to enable the identification of protein targets and specific binding sites of a wide variety of bioactive peptides in the future.

Statistical methods and its applications in Whey protein binding (Bos Taurus)

Milk is made up of two proteins, such as casein (80%) and whey (20%). These proteins, which include membrane globular proteins, glycoproteins, and lipoproteins, are mostly found in the outer layer of milk fat globule membranes. WP can be separated from the casein in milk or formed as a byproduct of cheese making and contains all nine essential amino acids with a low lactose content. Whey protein has many health benefits, including improving strength and body composition, promoting weight loss, boosting metabolism, stifling hunger, maintaining good health, avoiding nourishing the bones, reducing inflammation, promoting quick wound healing, lowering blood pressure, repairing and preserving muscle tissues etc. Many dairy and food-based industries eagerly explore the accurate retention time for the formation of health related new byproducts. As of date, there are very few studies available in the world literature citation database and too many micro and macro studies on WP are currently being undertaken globally, they provide insight into the binding of particular amino acids (Seq. peptides) and their accurate lag time of binding to the formation of "helixes and sheaths. In this paradigm, statistical tool are very important to determine average time and WP algorithms for analysis of seq amino acids and the metabolic pathway's action. Overall, the present research attempts to extrapolate the Seq peptide's binding capacity and its retention time for amino acids in order to fill the aforementioned research gap. For the model demonstration we used the commonly cited whey protein peptide (Seq) NCBS, which was considered to prove the hypothesis. The Markova two state random and Monte Carlo simulation (superimposed artificial neural network) models were formulated to extract transient probabilities and retention times of Seq peptides. As per the results, the binding capacity was found to be excellent with a good retention time (5 to 11.50 minutes) in cross-linked and unlinked cases (10 to 13.50 minutes). Bioinformatics, the dairy industry, and life scientists will find these more recent discoveries to be very helpful for measuring likelihoods and transient probabilities of binding.

Identification and evaluation of potential inhibitor molecules against TcyA from Candidatus Liberibacter asiaticus

Of the two putative amino acid binding periplasmic receptors of ABC transporter family in Candidatus Liberibacter asiaticus (CLas), cystine binding receptor (CLasTcyA) has been shown to mainly express in phloem of citrus plant and is a target for inhibitor development. The crystal structure of CLasTcyA in complex with substrates has been reported earlier. The present work reports the identification and evaluation of potential candidates for their inhibitory potential against CLasTcyA. Among many compounds, selected through virtual screening, and MD simulation, pimozide, clidinium, sulfasalazine and folic acid showed significantly higher affinities and stability in complex with CLasTcyA. The SPR studies with CLasTcyA revealed significantly higher binding affinities for pimozide and clidinium (Kd, 2.73 nM and 70 nM, respectively) as compared to cystine (Kd, 1.26 µM). The higher binding affinities could be attributed to significantly increased number of interactions in the binding pocket as evident from the crystal structures of CLasTcyA in complex with pimozide and clidinium as compared to cystine. The CLasTcyA possess relatively large binding pocket where bulkier inhibitors fit quite well. In planta studies, carried out to assess the effect of inhibitors on HLB infected Mosambi plants, showed significant reduction in CLas titre in plants treated with inhibitors as compared to control plants. The results showed that pimozide exhibited higher efficiency as compared to clidinium in reducing CLas titre in treated plants. Our results showed that the inhibitor development against critical proteins like CLasTcyA can be an important strategy in management of HLB.

Genistein - characterization of the molecule, similarity to estradiol and pharmacological potential

In recent years, the scientific world has become more interested in genistein. It has been the subject of extensive research for its potential in treating various diseases and as a functional food. The medical benefits of genistein are well documented in the literature. Several studies have been performed to better understand the mechanisms of its beneficiary effects on health and to improve its pharmacokinetic and pharmacodynamic parameters. It has been approved for relieving menopausal symptoms and has received attention for its use in the treatment of inflammatory and age-related disorders, cancer, metabolic illnesses, genetic disorders, and skin care. Genistein shows considerable similarity to endogenous estradiol. It is classified in the group known as phytoestrogens which exhibit properties corresponding to estrogen in the human body. The estrogenic activity resulting from the aforementioned similarity in the appearance of genistein and estradiol molecules makes it possible for genistein to act as both an estrogen agonist and antagonist, depending on the number of endogenous hormones present in the environment in which it is found and the type of tissue. The similarity of the chemical structure of genistein and estradiol and interactions occurring between estradiol and genistein and the amino acid binding site of the estrogen receptors were analyzed. Further controlled trials are needed to determine the efficacy and safety of genistein. Future research will focus on enhancing its bioavailability through structural modification and innovative delivery methods and conducting human trials to confirm its biological and pharmacological effects.

Structural insights into CodY activation and DNA recognition.

Virulence factors enable pathogenic bacteria to infect host cells, establish infection, and contribute to disease progressions. In Gram-positive pathogens such as Staphylococcus aureus (Sa) and Enterococcus faecalis (Ef), the pleiotropic transcription factor CodY plays a key role in integrating metabolism and virulence factor expression. However, to date, the structural mechanisms of CodY activation and DNA recognition are not understood. Here, we report the crystal structures of CodY from Sa and Ef in their ligand-free form and their ligand-bound form complexed with DNA. Binding of the ligands-branched chain amino acids and GTP-induces conformational changes in the form of helical shifts that propagate to the homodimer interface and reorient the linker helices and DNA binding domains. DNA binding is mediated by a non-canonical recognition mechanism dictated by DNA shape readout. Furthermore, two CodY dimers bind to two overlapping binding sites in a highly cooperative manner facilitated by cross-dimer interactions and minor groove deformation. Our structural and biochemical data explain how CodY can bind a wide range of substrates, a hallmark of many pleiotropic transcription factors. These data contribute to a better understanding of the mechanisms underlying virulence activation in important human pathogens.

Aryl Crown Ethers Based on d‐Glucose Scaffold – Highly Selective Receptors of Amino Acid Ester Hydrochlorides

AbstractAmino acids are important biomolecules with a broad scope of applications in chemical and biological sciences. Their functions and properties depend on their absolute configuration. Therefore, methods for chiral recognition and separation of amino acids are highly sought after. For the purposes of diagnostic and medicinal applications chiral recognition of amino acids in water is particularly relevant. However synthetic receptors for enantioselective binding of amino acids in aqueous media are rare. Recently we reported a d‐glucose‐based crown ether for chiral recognition of amino acid esters in water. We achieved enantioselectivities towards amino acids with hydrophobic sidechains which were among the highest ever reported for a small molecule receptor. The binding affinities were however moderate. Herein we disclose analogs of that receptor, containing aryl functionalities in the crown ether fragment. The new receptors show considerably improved binding affinities for amino acid ester hydrochlorides in water, while retaining high enantio‐ or chemoselectivities.

In-vitro antidiabetic activity, theoretical investigation by DFT and molecular docking of mono oxo vanadyl (IV) azomethine macromolecule

Prospective antidiabetic applicant [VO(IV)HBDB] was synthesized qualitatively and rapidly, spending HBDB of the mode N, N′-bis (2-hydroxy benzylidene)-1,2-diaminobenzene/Salophen a well familiar Schiff base with myriad property. Interesting and valuable details of physical and electronic properties, band gap energy, electronic configuration, and NLO possessions of the complex were reported. The complex consent with extraordinary NLO property accords with first-order hyperpolarizability. The impressiveness of the monooxo Vanadyl complex is elevated further by biological applications. The antibacterial evaluation accounts that [VO(IV)HBDB] shows greater activity than HBDB. DPPH scavenging report demonstrates that [VO(IV)HBDB] exhibits greater antioxidant potential than standard assay. Subsequently, in-vitro antidiabetic activity with α-glucosidase enzyme was also excellent. Molecular docking with α-glucosidase protein of PDB id: 3 WY1 illustrates greater binding energy of about −12.3 kcal/mol defined for [VO(IV)HBDB] than HBDB roughly −7.6 kcal/mol with more amino acid binding residues. The above-disclosed findings of HBDB and its complex firmly sustenance the biochemists and pharmacological field.

Guanidine Acetic Acid Alters Tissue Bound Amino Acid Profiles and Oxidative Status in Finishing Pigs.

This study aims to investigate the effects of guanidine acetic acid (GAA) on carcass traits, plasma biochemical parameters, tissue antioxidant capacity, and tissue-bound amino acid contents in finishing pigs. Seventy-two 140-day-old (body weight 86.59 ± 1.16 kg) crossbred pigs (Duroc × Landrace × Large White) were randomly assigned into four treatments with six replicate pens and three pigs per pen, which were fed the basal diets supplemented with 0, 0.05%, 0.10%, or 0.15% GAA, respectively. The plasma glucose concentration decreased, and creatine kinase activity and levels of GAA and creatine increased with the dietary GAA concentration. GAA linearly improved creatine content in the longissimus thoracis muscle (LM) and heart. The activities of superoxide dismutase, total antioxidant capacity, and glutathione peroxidase increased linearly in tissue or/and plasma, while the contents of malondialdehyde and protein carbonyl decreased linearly. GAA improved the contents of multiple-bound amino acids (such as proline or isoleucine) in the myocardium and LM. In conclusion, GAA enhanced the plasma biochemical parameters, oxidative status, and bound amino acid profiles of the heart and LM in finishing pigs.

De Novo Computational Design of a Lipase with Hydrolysis Activity towards Middle-Chained Fatty Acid Esters.

Innovations in biocatalysts provide great prospects for intolerant environments or novel reactions. Due to the limited catalytic capacity and the long-term and labor-intensive characteristics of mining enzymes with the desired functions, de novo enzyme design was developed to obtain industrial application candidates in a rapid and convenient way. Here, based on the catalytic mechanisms and the known structures of proteins, we proposed a computational protein design strategy combining de novo enzyme design and laboratory-directed evolution. Starting with the theozyme constructed using a quantum-mechanical approach, the theoretical enzyme-skeleton combinations were assembled and optimized via the Rosetta "inside-out" protocol. A small number of designed sequences were experimentally screened using SDS-PAGE, mass spectrometry and a qualitative activity assay in which the designed enzyme 1a8uD1 exhibited a measurable hydrolysis activity of 24.25 ± 0.57 U/g towards p-nitrophenyl octanoate. To improve the activity of the designed enzyme, molecular dynamics simulations and the RosettaDesign application were utilized to further optimize the substrate binding mode and amino acid sequence, thus keeping the residues of theozyme intact. The redesigned lipase 1a8uD1-M8 displayed enhanced hydrolysis activity towards p-nitrophenyl octanoate-3.34 times higher than that of 1a8uD1. Meanwhile, the natural skeleton protein (PDB entry 1a8u) did not display any hydrolysis activity, confirming that the hydrolysis abilities of the designed 1a8uD1 and the redesigned 1a8uD1-M8 were devised from scratch. More importantly, the designed 1a8uD1-M8 was also able to hydrolyze the natural middle-chained substrate (glycerol trioctanoate), for which the activity was 27.67 ± 0.69 U/g. This study indicates that the strategy employed here has great potential to generate novel enzymes exhibiting the desired reactions.