SciCombinator

Discover the most talked about and latest scientific content & concepts.

Concept: Enzyme

440

Flowers of the hop plant provide both bitterness and “hoppy” flavor to beer. Hops are, however, both a water and energy intensive crop and vary considerably in essential oil content, making it challenging to achieve a consistent hoppy taste in beer. Here, we report that brewer’s yeast can be engineered to biosynthesize aromatic monoterpene molecules that impart hoppy flavor to beer by incorporating recombinant DNA derived from yeast, mint, and basil. Whereas metabolic engineering of biosynthetic pathways is commonly enlisted to maximize product titers, tuning expression of pathway enzymes to affect target production levels of multiple commercially important metabolites without major collateral metabolic changes represents a unique challenge. By applying state-of-the-art engineering techniques and a framework to guide iterative improvement, strains are generated with target performance characteristics. Beers produced using these strains are perceived as hoppier than traditionally hopped beers by a sensory panel in a double-blind tasting.

Concepts: DNA, Carbon dioxide, Metabolism, Enzyme, Taste, Brewing, Beer, Hops

401

The restoration of dentine lost in deep caries lesions in teeth is a routine and common treatment that involves the use of inorganic cements based on calcium or silicon-based mineral aggregates. Such cements remain in the tooth and fail to degrade and thus normal mineral volume is never completely restored. Here we describe a novel, biological approach to dentine restoration that stimulates the natural formation of reparative dentine via the mobilisation of resident stem cells in the tooth pulp. Biodegradable, clinically-approved collagen sponges are used to deliver low doses of small molecule glycogen synthase kinase (GSK-3) antagonists that promote the natural processes of reparative dentine formation to completely restore dentine. Since the carrier sponge is degraded over time, dentine replaces the degraded sponge leading to a complete, effective natural repair. This simple, rapid natural tooth repair process could thus potentially provide a new approach to clinical tooth restoration.

Concepts: Enzyme, Animal, Teeth, Tooth, Dental caries, Portland cement, GSK-3, GSK3B

354

We report the discovery that strains ofStaphylococcus epidermidisproduce 6-N-hydroxyaminopurine (6-HAP), a molecule that inhibits DNA polymerase activity. In culture, 6-HAP selectively inhibited proliferation of tumor lines but did not inhibit primary keratinocytes. Resistance to 6-HAP was associated with the expression of mitochondrial amidoxime reducing components, enzymes that were not observed in cells sensitive to this compound. Intravenous injection of 6-HAP in mice suppressed the growth of B16F10 melanoma without evidence of systemic toxicity. Colonization of mice with anS. epidermidisstrain producing 6-HAP reduced the incidence of ultraviolet-induced tumors compared to mice colonized by a control strain that did not produce 6-HAP.S. epidermidisstrains producing 6-HAP were found in the metagenome from multiple healthy human subjects, suggesting that the microbiome of some individuals may confer protection against skin cancer. These findings show a new role for skin commensal bacteria in host defense.

Concepts: DNA, Cancer, Bacteria, Adenosine triphosphate, Enzyme, Tumor, Neoplasm, DNA polymerase I

310

A CAPN1 missense mutation in Parson Russell Terrier dogs is associated with spinocerebellar ataxia. We now report that homozygous or heterozygous CAPN1-null mutations in humans result in cerebellar ataxia and limb spasticity in four independent pedigrees. Calpain-1 knockout (KO) mice also exhibit a mild form of ataxia due to abnormal cerebellar development, including enhanced neuronal apoptosis, decreased number of cerebellar granule cells, and altered synaptic transmission. Enhanced apoptosis is due to absence of calpain-1-mediated cleavage of PH domain and leucine-rich repeat protein phosphatase 1 (PHLPP1), which results in inhibition of the Akt pro-survival pathway in developing granule cells. Injection of neonatal mice with the indirect Akt activator, bisperoxovanadium, or crossing calpain-1 KO mice with PHLPP1 KO mice prevented increased postnatal cerebellar granule cell apoptosis and restored granule cell density and motor coordination in adult mice. Thus, mutations in CAPN1 are an additional cause of ataxia in mammals, including humans.

Concepts: DNA, Neuron, Mutation, Enzyme, Cerebellum, Granule cell, Point mutation, Jack Russell Terrier

285

High-protein (HP) intake during weight loss (WL) therapy is often recommended because it reduces the loss of lean tissue mass. However, HP intake could have adverse effects on metabolic function, because protein ingestion reduces postprandial insulin sensitivity. In this study, we compared the effects of ∼10% WL with a hypocaloric diet containing 0.8 g protein/kg/day and a hypocaloric diet containing 1.2 g protein/kg/day on muscle insulin action in postmenopausal women with obesity. We found that HP intake reduced the WL-induced decline in lean tissue mass by ∼45%. However, HP intake also prevented the WL-induced improvements in muscle insulin signaling and insulin-stimulated glucose uptake, as well as the WL-induced adaptations in oxidative stress and cell structural biology pathways. Our data demonstrate that the protein content of a WL diet can have profound effects on metabolic function and underscore the importance of considering dietary macronutrient composition during WL therapy for people with obesity.

Concepts: Protein, Nutrition, Enzyme, Insulin, Diabetes mellitus, Obesity, Adipose tissue, Metabolic syndrome

279

Yeast and cancer cells share the unusual characteristic of favoring fermentation of sugar over respiration. We now reveal an evolutionary conserved mechanism linking fermentation to activation of Ras, a major regulator of cell proliferation in yeast and mammalian cells, and prime proto-oncogene product. A yeast mutant (tps1∆) with overactive influx of glucose into glycolysis and hyperaccumulation of Fru1,6bisP, shows hyperactivation of Ras, which causes its glucose growth defect by triggering apoptosis. Fru1,6bisP is a potent activator of Ras in permeabilized yeast cells, likely acting through Cdc25. As in yeast, glucose triggers activation of Ras and its downstream targets MEK and ERK in mammalian cells. Biolayer interferometry measurements show that physiological concentrations of Fru1,6bisP stimulate dissociation of the pure Sos1/H-Ras complex. Thermal shift assay confirms direct binding to Sos1, the mammalian ortholog of Cdc25. Our results suggest that the Warburg effect creates a vicious cycle through Fru1,6bisP activation of Ras, by which enhanced fermentation stimulates oncogenic potency.Yeast and cancer cells both favor sugar fermentation in aerobic conditions. Here the authors describe a conserved mechanism from yeast to mammals where the glycolysis intermediate fructose-1,6-bisphosphate binds Cdc25/Sos1 and couples increased glycolytic flux to increased Ras proto-oncoprotein activity.

Concepts: Bacteria, Adenosine triphosphate, Enzyme, Glucose, Yeast, Cell cycle, Glycolysis, Ethanol fermentation

264

Pancreatic adenocarcinomas (PAs) have very poor prognoses even when surgery is possible. Currently, there are no tissular biomarkers to predict long-term survival in patients with PA. The aims of this study were to (1) describe the metabolome of pancreatic parenchyma (PP) and PA, (2) determine the impact of neoadjuvant chemotherapy on PP and PA, and (3) find tissue metabolic biomarkers associated with long-term survivors, using metabolomics analysis.

Concepts: Metabolism, Enzyme, Adenocarcinoma, Pancreatic cancer, Digestion, Metabolomics, Metabolome, Antimetabolite

238

This paper describes a method of generating three-dimensional (3D) cell-laden microstructures by applying the principle of origami folding technique and cell traction force (CTF). We harness the CTF as a biological driving force to fold the microstructures. Cells stretch and adhere across multiple microplates. Upon detaching the microplates from a substrate, CTF causes the plates to lift and fold according to a prescribed pattern. This self-folding technique using cells is highly biocompatible and does not involve special material requirements for the microplates and hinges to induce folding. We successfully produced various 3D cell-laden microstructures by just changing the geometry of the patterned 2D plates. We also achieved mass-production of the 3D cell-laden microstructures without causing damage to the cells. We believe that our methods will be useful for biotechnology applications that require analysis of cells in 3D configurations and for self-assembly of cell-based micro-medical devices.

Concepts: DNA, Gene, Causality, Enzyme, Organism, Cell biology, Biotechnology, Cell wall

220

We have developed an implantable fuel cell that generates power through glucose oxidation, producing 3.4 μW cm(-2) steady-state power and up to 180 μW cm(-2) peak power. The fuel cell is manufactured using a novel approach, employing semiconductor fabrication techniques, and is therefore well suited for manufacture together with integrated circuits on a single silicon wafer. Thus, it can help enable implantable microelectronic systems with long-lifetime power sources that harvest energy from their surrounds. The fuel reactions are mediated by robust, solid state catalysts. Glucose is oxidized at the nanostructured surface of an activated platinum anode. Oxygen is reduced to water at the surface of a self-assembled network of single-walled carbon nanotubes, embedded in a Nafion film that forms the cathode and is exposed to the biological environment. The catalytic electrodes are separated by a Nafion membrane. The availability of fuel cell reactants, oxygen and glucose, only as a mixture in the physiologic environment, has traditionally posed a design challenge: Net current production requires oxidation and reduction to occur separately and selectively at the anode and cathode, respectively, to prevent electrochemical short circuits. Our fuel cell is configured in a half-open geometry that shields the anode while exposing the cathode, resulting in an oxygen gradient that strongly favors oxygen reduction at the cathode. Glucose reaches the shielded anode by diffusing through the nanotube mesh, which does not catalyze glucose oxidation, and the Nafion layers, which are permeable to small neutral and cationic species. We demonstrate computationally that the natural recirculation of cerebrospinal fluid around the human brain theoretically permits glucose energy harvesting at a rate on the order of at least 1 mW with no adverse physiologic effects. Low-power brain-machine interfaces can thus potentially benefit from having their implanted units powered or recharged by glucose fuel cells.

Concepts: Carbon dioxide, Enzyme, Hydrogen, Redox, Electrochemistry, Carbon, Electrochemical cell, Electrolysis

186

BACKGROUND: Autism spectrum disorders (ASDs) are relatively common neurodevelopmental conditions whose biological basis has been incompletely determined. Several biochemical markers have been associated with ASDs, but there is still no laboratory test for these conditions. METHODS: We analyzed the metabolic profile of lymphoblastoid cell lines from 137 patients with neurodevelopmental disorders with or without ASDs and 78 normal individuals, using Biolog Phenotype MicroArrays. RESULTS: Metabolic profiling of lymphoblastoid cells revealed that the 87 patients with ASD as a clinical feature, as compared to the 78 controls, exhibited on average reduced generation of NADH when tryptophan was the sole energy source. The results correlated with the behavioral traits associated with either syndromal or non-syndromal autism, independent of the genetic background of the individual. The low level of NADH generation in the presence of tryptophan was not observed in cell lines from non-ASD patients with intellectual disability, schizophrenia or conditions exhibiting several similarities with syndromal autism except for the behavioral traits. Analysis of a previous small gene expression study found abnormal levels for some genes involved in tryptophan metabolic pathways in 10 patients. CONCLUSIONS: Tryptophan is a precursor of important compounds, such as serotonin, quinolinic acid, and kynurenic acid, which are involved in neurodevelopment and synaptogenesis. In addition, quinolinic acid is the structural precursor of NAD+, a critical energy carrier in mitochondria. Also, the serotonin branch of the tryptophan metabolic pathway generates NADH. Lastly, the levels of quinolinic and kynurenic acid are strongly influenced by the activity of the immune system. Therefore, decreased tryptophan metabolism may alter brain development, neuroimmune activity and mitochondrial function. Our finding of decreased tryptophan metabolism appears to provide a unifying biochemical basis for ASDs and perhaps an initial step in the development of a diagnostic assay for ASDs.

Concepts: Bacteria, Metabolism, Adenosine triphosphate, Enzyme, Organism, Mitochondrion, Autism, Neural development