Cryptic enzymatic assembly of peptides armed with β-lactone warheads

Nature has evolved biosynthetic pathways to molecules possessing reactive warheads that inspired the development of many therapeutic agents, including penicillin antibiotics. Peptides armed with electrophilic warheads have proven to be particularly effective covalent inhibitors, providing essential antimicrobial, antiviral and anticancer agents. Here we provide a full characterization of the pathways that nature deploys to assemble peptides with β-lactone warheads, which are potent proteasome inhibitors with promising anticancer activity. Warhead assembly involves a three-step cryptic methylation sequence, which is likely required to reduce unfavorable electrostatic interactions during the sterically demanding β-lactonization. Amide-bond synthetase and adenosine triphosphate (ATP)-grasp enzymes couple amino acids to the β-lactone warhead, generating the bioactive peptide products. After reconstituting the entire pathway to β-lactone peptides in vitro, we go on to deliver a diverse range of analogs through enzymatic cascade reactions. Our approach is more efficient and cleaner than the synthetic methods currently used to produce clinically important warhead-containing peptides.

Biopanning, Heterologous Expression, and Characterization of a Shark-Derived Single-Domain Antibody Fusion Protein against Pancreatic Lipase

Nowadays, obesity severely impacts human health and is the fifth leading risk factor that leads to death globally. Pancreatic lipase (PL) inhibitors have attracted extensive attention owing to their role in effective prevention and treatment of obesity. Here, a shark-derived single-domain antibody fusion protein was used to inhibit PL for the first time. After biopanning, the heterologous expression system pET28a-SUMO-D2 was constructed using the method of double restriction enzyme digestion and T4 ligase to achieve the soluble expression of the PL-specific antibody gene D2. According to the calculation of protein concentration, the final expression of fusion protein PL-D2S was 1.183 mg per liter of Luria Bertani broth. The binding ability of the soluble fusion protein PL-D2S to PL was identified. Enzyme-linked immunosorbent assay results showed that the fusion protein PL-D2S exhibited a strong binding affinity to PL. The experimental results of PL inhibition of PL-D2S in vitro showed that the fusion protein could significantly inhibit the activity of PL, with an IC₅₀ of 404 μg/mL. Our study shows that the fusion protein PL-D2S is a potential PL inhibitor to prevent and treat obesity.

Access to N-CF3 Formamides by Reduction of N-CF3 Carbamoyl Fluorides

The departure into unknown chemical space is essential for the discovery of new properties and function. We herein report the first synthetic access to N-trifluoromethylated formamides. The method involves the reduction of bench-stable NCF₃ carbamoyl fluorides and is characterized by operational simplicity and mildness, tolerating a broad range of functional groups as well as stereocenters. The newly made N-CF₃ formamide motif proved to be highly robust and compatible with diverse chemical transformations, underscoring its potential as building block in complex functional molecules.

Inhibitory activities of grape bioactive compounds against enzymes linked with human diseases

A quest for identification of novel, safe and efficient natural compounds, as additives in the modern food and cosmetic industries, has been prompted by concerns about toxicity and side effects of synthetic products. Plant phenolic compounds are one of the most documented natural products due to their multifarious biological applications. Grape (Vitis vinifera) is an important source of phenolic compounds such as phenolic acids, tannins, quinones, coumarins and, most importantly, flavonoids/flavones. This review crisply encapsulates enzyme inhibitory activities of various grape polyphenols towards different key human-ailment-associated enzymes: xanthine oxidase (gout), tyrosinase (hyperpigmentation), α-amylase and α-glucosidase (diabetes mellitus), pancreatic lipase (obesity), cholinesterase (Alzheimer's disease), angiotensin i-converting enzymes (hypertension), α-synuclein (Parkinson's disease) and histone deacetylase (various diseases). The review also depicts the enzyme inhibitory mechanism of various grape polyphenols and briefly discusses their stature as potential therapeutic and drug development candidates. KEY POINTS: • Nineteen major bioactive polyphenols from the grape/grape products and their disease targets are presented • Sixty-two important polyphenols as enzyme inhibitors from grape/grape products are presented • A thorough description and graphical presentation of biological significance of polyphenols against various diseases.

Dihydromyricetin Imbues Antiadipogenic Effects on 3T3-L1 Cells via Direct Interactions with 78-kDa Glucose-Regulated Protein

BACKGROUND

Obesity is among the most serious public health problems worldwide, with few safe pharmaceutical interventions. Natural products have become an important source of potential anti-obesity therapeutics. Dihydromyricetin (DHM) exerts antidiabetic effects. The biochemical target of DHM, however, has been unknown. It is crucial to identify the biochemical target of DHM for elucidating its physiological function and therapeutic value.

OBJECTIVES

The objective of this study was to identify the biochemical target of DHM.

METHODS

An abundant antiadipogenic flavanonol was extracted from the herbal plant Ampelopsis grossedentata through bioassay-guided fractionation and characterized with high-resolution LC-MS and 1H and 13C nuclear magnetic resonance. Antiadipogenic experiments were done with mouse 3T3-L1 preadipocytes. A biochemical target of the chemical of interest was identified with drug affinity responsive target stability assay. Direct interactions between the chemical of interest and the protein target in vitro were predicted with molecular docking and subsequently confirmed with surface plasmon resonance. Expression levels of peroxisome proliferator-activated receptor γ (PPARγ), which is associated with 78-kDa glucose-regulated protein (GRP78), were measured with real-time qPCR.

RESULTS

DHM was isolated, purified, and structurally characterized. Cellular studies showed that DHM notably reduced intracellular oil droplet formation in 3T3-L1 cells with a median effective concentration of 294 μM (i.e., 94 μg/mL). DHM targeted the ATP binding site of GRP78, which is associated with adipogenesis. An equilibrium dissociation constant between DHM and GRP78 was 21.8 μM. In 3T3-L1 cells upon treatment with DHM at 50 μM (i.e., 16 μg/mL), the expression level of PPARγ was downregulated to 53.9% of the solvent vehicle control's level.

CONCLUSIONS

DHM targets GRP78 in vitro. DHM is able to reduce lipid droplet formation in 3T3-L1 cells through a mode of action that is plausibly associated with direct interactions between GRP78 and DHM, which is a step forward in determining potential applications of DHM as an anti-obesity agent.

Pancreatic lipase inhibitors: The road voyaged and successes

Human pancreatic lipase (triacylglycerol acyl hydrolase EC3.1.1.3) is the most widely studied member of the human lipase superfamily related to carboxyl esterase. It is secreted from the acinar cell of pancreas and has strong preference for triacylglycerides over cholesterol esters, phospholipids, and galactolipids. Apart from the hydrolysis of triacylglycerides, pancreatic lipase may cause the hydrolysis of retinyl esters in vivo. So, it is very much evidenced that pancreatic lipase with its cofactor colipase has prominent role in efficient digestion of dietary fat. Hence, the modulation of human pancreatic lipase may represent a new insight in the discovery of a number of therapeutics that can inhibit the absorption of fat in body and can be used in obesity and other related metabolic disorders. Even, the only Food and drug administration (FDA) approved antiobesity drug, orlistat, is also an inhibitor of pancreatic lipase. This review summarizes studies about structure, mechanistic approach of pancreatic lipase enzyme while emphasizing on the various synthetic pancreatic lipase inhibitors with their structure activity relationship (SAR).

Prominent and emerging anti-diabetic molecular targets

Diabetes is on the rise across the globe affecting more than 463 million people and crucially increasing morbidities of diabetes-associated diseases. Urgent and immense actions are needed to improve diabetes prevention and treatment. Regarding the correlation of diabetes with many associated diseases, inhibition of the disease progression is more crucial than controlling symptoms. Currently, anti-diabetic drugs are accompanied by undesirable side-effects and target confined types of biomolecules. Thus, extensive research is demanding to identify novel disease mechanisms and molecular targets as probable candidates for effective treatment of diabetes. This review discusses the conventional molecule targets that have been applied for their therapeutic rationale in treatment of diabetes. Further, the emerging and prospective molecular targets for the future focus of library screenings are presented.

Exploring Aurone Derivatives as Potential Human Pancreatic Lipase Inhibitors through Molecular Docking and Molecular Dynamics Simulations

Inhibition of human pancreatic lipase, a crucial enzyme in dietary fat digestion and absorption, is a potent therapeutic approach for obesity treatment. In this study, human pancreatic lipase inhibitory activity of aurone derivatives was explored by molecular modeling approaches. The target protein was human pancreatic lipase (PDB ID: 1LPB). The 3D structures of 82 published bioactive aurone derivatives were docked successfully into the protein catalytic active site, using AutoDock Vina 1.5.7.rc1. Of them, 62 compounds interacted with the key residues of catalytic trial Ser152-Asp176-His263. The top hit compound (A14), with a docking score of −10.6 kcal⋅mol⁻¹, was subsequently submitted to molecular dynamics simulations, using GROMACS 2018.01. Molecular dynamics simulation results showed that A14 formed a stable complex with 1LPB protein via hydrogen bonds with important residues in regulating enzyme activity (Ser152 and Phe77). Compound A14 showed high potency for further studies, such as the synthesis, in vitro and in vivo tests for pancreatic lipase inhibitory activity.

Enhanced production of lipstatin from mutant of Streptomyces toxytricini and fed-batch strategies under submerged fermentation

Streptomyces toxytricini produces bioactive metabolite recognized as lipstatin and its intermediate orlistat. The main focus of this study is to enhance lipstatin production by strain improvement and precursor feeding. In this study, strain improvement to enhance the production of lipstatin was carried out by different doses (50, 100, 150, 200, and 250 Gy) of gamma radiation and precursors (Linoleic acid, Oleic acid, and l-Leucine). Screening showed that the highest yield of lipstatin (4.58 mg/g) was produced by mutant designated as SRN 7. The production of lipstatin (5.011 mg/g) increased significantly when the medium was supplemented with ratio 1:1.5 (linoleic acid + oleic acid). The addition of 1.5% l-Leucine leads to further increment in the production of lipstatin (5.765 mg/g). The addition of 10% soy flour in the culture medium resulted in the maximum production of lipstatin to 5.886 mg/g.

MetaMed: Linking Microbiota Functions with Medicine Therapeutics

Understanding how the human microbiome affects human health has consequences for treating disease and minimizing unwanted side effects in clinical research.

Understanding how the human microbiome affects human health has consequences for treating disease and minimizing unwanted side effects in clinical research. Here, we present MetaMed (http://metamed.rwebox.com/index), a novel and integrative system-wide correlation mapping system to link bacterial functions and medicine therapeutics, providing novel hypotheses for deep investigation of microbe therapeutic effects on human health. Furthermore, comprehensive relationships between microbes living in the environment and drugs were discovered, providing a rich source for discovering microbiota metabolites with great potential for pharmaceutical applications.

A KAS-III Heterodimer in Lipstatin Biosynthesis Nondecarboxylatively Condenses C8 and C14 Fatty Acyl-CoA Substrates by a Variable Mechanism during the Establishment of a C22 Aliphatic Skeleton

β-Ketoacyl-acyl carrier protein synthase-III (KAS-III) and its homologues are thiolase-fold proteins that typically behave as homodimers functioning in diverse thioester-based reactions for C-C, C-O, or C-N bond formation. Here, we report an exception observed in the biosynthesis of lipstatin. During the establishment of the C₂₂ aliphatic skeleton of this β-lactone lipase inhibitor, LstA and LstB, which both are KAS-III homologues but phylogenetically distinct from each other, function together by forming an unusual heterodimer to catalyze a nondecarboxylating Claisen condensation of C₈ and C₁₄ fatty acyl-CoA substrates. The resulting C₂₂ α-alkyl β-ketoacid, which is unstable and tends to be spontaneously decarboxylated to a shunt C₂₁ hydrocarbon product, is transformed by the stereoselective β-ketoreductase LstD into a relatively stable C₂₂ α-alkyl β-hydroxyacid for further transformation. LstAB activity tolerates changes in the stereochemistry, saturation degree, and thioester form of both long-chain fatty acyl-CoA substrates. This flexibility, along with the characterization of catalytic residues, benefits our investigations into the individual roles of the two KAS-III homologues in the heterodimer-catalyzed reactions. The large subunit LstA contains a characteristic Cys-His-Asn triad and likely reacts with C₈ acyl-CoA to form an acyl-Cys enzyme intermediate. In contrast, the small subunit LstB lacks this triad but possesses a catalytic Glu residue, which can act on the C₈ acyl-Cys enzyme intermediate in a substrate-dependent manner, either as a base for Cα deprotonation or as a nucleophile for a Michael-type addition-initiated cascade reaction, to produce an enolate anion for head-to-head assembly with C₁₄ acyl-CoA through a unidirectional nucleophilic substitution. Uncovering LstAB catalysis draws attention to thiolase-fold proteins that are noncanonical in both active form and catalytic reaction/mechanism. LstAB homologues are widespread in bacteria and remain to be functionally assigned, generating great interest in their corresponding products and associated biological functions.

Diversifying of Chemical Structure of Native Monascus Pigments

Red Yeast Rice, produced by solid state fermentation of Monascus species on rice, is a traditional food additive and traditional Chinese medicine. With the introduction of modern microbiology and biotechnology to the traditional edible filamentous fungi Monascus species, it has been revealed that the production of red colorant by fermentation of Monascus species involves the biosynthesis of orange Monascus pigments and further chemical modification of orange Monascus pigments into the corresponding derivates with various amine residues. Further study indicates that non-Monascus species also produce Monascus pigments as well as Monascus-like pigments. Based on the chemical modification of orange Monascus pigments, the diversification of native Monascus pigments, including commercial food additives of Red Monascus Pigments^® and Yellow Monascus Pigments^® in Chinese market, was reviewed. Furthermore, Monascus pigments as well as their derivates as enzyme inhibitors for anti-obesity, hyperlipidemia, and hyperglycemia was also summarized.

Implication of mutagenesis and precursor supplementation towards the enhancement of lipstatin (an antiobesity agent) biosynthesis through submerged fermentation using Streptomyces toxytricini

In the present study, lipstatin production was studied from different mutants of Streptomyces toxytricini which were developed using ultraviolet radiation (exposure time 30 s, 1, 2, 5 and 10 min), ethyl methane sulfonte, methyl methane sulfonate (MMS) and N-methyl-N'-intro-N-nitrosoguanidine (NTG) treatments (50, 100, 200, 500, 1000 µM, respectively). Highest yielding mutants were provided precursor supplementation of citric acid, thiamine and biotin (each 1 g/L) at idiophase for further enhancement in the production of lipstatin. Screened mutants produced biomass in the range of 5.8-7.16 g/L which were lesser than control. Screened mutants also exhibited pellet morphology in submerged culture. Out of these mutants, NTG8 mutant produced highest amount of lipstatin (1383.25 mg/L) with 9.606 mg/L/h productivity. Precursor supplementation to this mutant further increased the production to 2387.81 mg/L. Mutant was validated in 5 L bioreactor and lipstatin production was enhanced to 2519.34 mg/L.

Rh-Catalyzed Conjugate Addition of Aryl and Alkenyl Boronic Acids to α-Methylene-β-lactones: Stereoselective Synthesis of trans-3,4-Disubstituted β-Lactones

A one-step preparation of 3,4-disubstituted β-lactones through Rh-catalyzed conjugate addition of aryl or alkenyl boronic acids to α-methylene-β-lactones is described. The operationally simple, stereoselective transformation provides a broad range of β-lactones from individual α-methylene-β-lactone templates. This methodology allowed for a direct, final-step C-3 diversification of nocardiolactone, an antimicrobial natural product.

Mycelium transformation of Streptomyces toxytricini into pellet: Role of culture conditions and kinetics

The present study envisages the role of different carbon sources, nitrogen sources, metals, pH, inoculum volume and agitation rate in pellet formation of S. toxytricini at shake-flask level. It was found that galactose, ammonium sulphate, sodium nitrate, Cu²⁺, Zn²⁺, higher inoculum volume (5% v/v) and agitation rate at 300rpm caused significant reduction in pellet size (up to the range of 30μm-0.5mm) but biomass formations was also reduced subsequently. Interestingly diffused type of morphology was obtained in Fe²⁺ supplemented medium with reduced biomass (1.5gL^-1). Rheological study revealed that non-Newtonian behaviour of culture broth. Besides this, kinetics study was also made to understand the growth kinetics (0.39gL^-1h^-1), oxygen uptake rate (0.1146mgL^-1h^-1), and production of lipstatin (0.0072gh^-1).

Modulation of fatty acid metabolism and tricarboxylic acid cycle to enhance the lipstatin production through medium engineering in Streptomyces toxytricini

This work investigated the potential of medium engineering to obtain maximum biomass, non-conventional carbon sources for lipstatin production and modulation of tricarboxylic acid (TCA) cycle to promote lipstatin synthesis. It was found that 2:3 carbon and nitrogen ratio, produced maximum biomass of 7.9g/L in growth medium and 6.6g/L in pre-seed medium. Among the studied non-conventional carbon sources i.e., soya flour 40g/L and sesame oil 30mL/L were found producing 1109.37mg/L (1.24-fold of control) and 1196.75mg/L (1.34-fold of control) lipstatin respectively. Supplementation of TCA cycle intermediates revealed that NADH and succinic acid showed lipstatin production to 1132.99mg/L and 1171.10mg/L respectively. Experimental outcome was validated in 7L bioreactor and produced 2242.63mg/L lipstatin which was ∼14% higher than shake flask.