Screening of Yeast in Various Vineyard Soil and Study on Its Flavor Compounds from Brewing Grape Wine

In order to screen out Saccharomyces cerevisiae suitable for table grape fermentation, and compare it with commercial Saccharomyces cerevisiae in terms of fermentation performance and aroma producing substances, differences of fermentation flavor caused by different strains were discussed. In this experiment, yeast was isolated and purified from vineyard soil, 26s rDNA identification and fermentation substrate tolerance analysis were carried out, and the causes of flavor differences of wine were analyzed from three aspects: GC-MS, PCA and sensory evaluation. The results showed that strain S1 had the highest floral aroma fraction, corresponding to its high production of ethyl octanoate and other substances, and it had the characteristics of high sugar tolerance. The fruit sensory score of S3 wine was the highest among the six wines. Through exploration and analysis, it was found that compared with commercial Saccharomyces cerevisiae, the screened strains had more advantages in fermenting table grapes. The flavor of each wine was directly related to the growth characteristics and tolerance of its strains.

Decarboxylative, diastereoselective and exo-selective 1,3-dipolar cycloaddition for diversity-oriented construction of structurally spiro-[butyrolactone-pyrrolidine-chromanone] hybrids

Inspired by the chemistry and biology of butyrolactones, pyrrolidines and chromanones, herein we successfully developed a simple domino 1,3-dipolar cycloaddition of homoserine lactone-derived azomethine ylides for construction of biologically important spiro-[butyrolactone-pyrrolidine-chromanone] hybrids in the presence of the catalyst Et3N under mild conditions. It is based on the application of carboxylic acid activated chromones as dienophiles followed by a decarboxylation process. This reaction displayed good substrate tolerance and gave the desired products in moderate to good yields with high diastereoselectivities via an exo-transition state (up to 85% yield and >20:1 diastereomeric ratio). In particular, this is the first example of introduction of chromanone moiety into spiro [butyrolactone-pyrrolidine] frameworks, which might be valuable in medicinal chemistry.

Targeting of GLUT5 for Transporter-Mediated Drug-Delivery Is Contingent upon Substrate Hydrophilicity

Specific link between high fructose uptake and cancer development and progression highlighted fructose transporters as potential means to achieve GLUT-mediated discrimination between normal and cancer cells. The gained expression of fructose-specific transporter GLUT5 in various cancers offers a possibility for developing cancer-specific imaging and bioactive agents. Herein, we explore the feasibility of delivering a bioactive agent through cancer-relevant fructose-specific transporter GLUT5. We employed specific targeting of GLUT5 by 2,5-anhydro-D-mannitol and investigated several drug conjugates for their ability to induce cancer-specific cytotoxicity. The proof-of-concept analysis was carried out for conjugates of chlorambucil (CLB) in GLUT5-positive breast cancer cells and normal breast cells. The cytotoxicity of conjugates was assessed over 24 h and 48 h, and significant dependence between cancer-selectivity and conjugate size was observed. The differences were found to relate to the loss of GLUT5-mediated uptake upon increased conjugate size and hydrophobicity. The findings provide information on the substrate tolerance of GLUT5 and highlight the importance of maintaining appropriate hydrophilicity for GLUT-mediated delivery.

Tuning a bi-enzymatic cascade reaction in Escherichia coli to facilitate NADPH regeneration for ε-caprolactone production

Abstractε-Caprolactone is a monomer of poly(ε-caprolactone) which has been widely used in tissue engineering due to its biodegradability and biocompatibility. To meet the massive demand for this monomer, an efficient whole-cell biocatalytic approach was constructed to boost the ε-caprolactone production using cyclohexanol as substrate. Combining an alcohol dehydrogenase (ADH) with a cyclohexanone monooxygenase (CHMO) in Escherichia coli, a self-sufficient NADPH-cofactor regeneration system was obtained. Furthermore, some improved variants with the better substrate tolerance and higher catalytic ability to ε-caprolactone production were designed by regulating the ribosome binding sites. The best mutant strain exhibited an ε-caprolactone yield of 0.80 mol/mol using 60 mM cyclohexanol as substrate, while the starting strain only got a conversion of 0.38 mol/mol when 20 mM cyclohexanol was supplemented. The engineered whole-cell biocatalyst was used in four sequential batches to achieve a production of 126 mM ε-caprolactone with a high molar yield of 0.78 mol/mol.

Synthesis of Multi-Protein Complexes through Charge-Directed Sequential Activation of Tyrosine Residues

Site-selective protein-protein coupling has long been a goal of chemical biology research. In recent years, that goal has been realized to varying degrees through a number of techniques, including the use of tyrosinase-based coupling strategies. Early publications utilizing tyrosinase from <i>Agaricus bisporus</i> showed the potential to convert tyrosine residues into <i>ortho</i>-quinone functional groups, but this enzyme is challenging to produce recombinantly and suffers from some limitations in substrate scope. Initial screens of several tyrosinase candidates revealed that the tyrosinase from <i>Bacillus megaterium</i> (megaTYR) as an enzyme that possesses a broad substrate tolerance. We use the expanded substrate preference as a starting point for protein design experiments and show that single point mutants of megaTYR are capable of activating tyrosine residues in various sequence contexts. We leverage this new tool to enable the construction of protein trimers via a charge-directed sequential activation of tyrosine residues (CDSAT).

Synthesis of Multi-Protein Complexes through Charge-Directed Sequential Activation of Tyrosine Residues

Site-selective protein-protein coupling has long been a goal of chemical biology research. In recent years, that goal has been realized to varying degrees through a number of techniques, including the use of tyrosinase-based coupling strategies. Early publications utilizing tyrosinase from <i>Agaricus bisporus</i> showed the potential to convert tyrosine residues into <i>ortho</i>-quinone functional groups, but this enzyme is challenging to produce recombinantly and suffers from some limitations in substrate scope. Initial screens of several tyrosinase candidates revealed that the tyrosinase from <i>Bacillus megaterium</i> (megaTYR) as an enzyme that possesses a broad substrate tolerance. We use the expanded substrate preference as a starting point for protein design experiments and show that single point mutants of megaTYR are capable of activating tyrosine residues in various sequence contexts. We leverage this new tool to enable the construction of protein trimers via a charge-directed sequential activation of tyrosine residues (CDSAT).

Breakdown of 3-(allylsulfonio)propanoates in bacteria from the Roseobacter group yields garlic oil constituents

Two analogues of 3-(dimethylsulfonio)propanoate (DMSP), 3-(diallylsulfonio)propanoate (DAllSP), and 3-(allylmethylsulfonio)propanoate (AllMSP), were synthesized and fed to marine bacteria from the Roseobacter clade. These bacteria are able to degrade DMSP into dimethyl sulfide and methanethiol. The DMSP analogues were also degraded, resulting in the release of allylated sulfur volatiles known from garlic. For unknown compounds, structural suggestions were made based on their mass spectrometric fragmentation pattern and confirmed by the synthesis of reference compounds. The results of the feeding experiments allowed to conclude on the substrate tolerance of DMSP degrading enzymes in marine bacteria.

Limited Hydrolysis of Polysialic Acid by Human Neuraminidase Enzymes

Regulation of sialic acids by human neuraminidase (hNEU) enzymes is important to many biological processes. Defining hNEU substrate tolerance can help to elucidate the roles of these enzymes in regulating sialosides in human health and disease. Polysialic acid (polySia) is a polyanion of α(2→8) linked sialic acids with roles in nervous, reproductive, and immune systems and is dysregulated in some malignancies and mental disorders. The unique chemical properties of this polymer, which include an enhanced susceptibility to acid-catalyzed hydrolysis, have hampered its study. Herein we describe the first<i> </i>systematic study of hNEU isoenzyme activity towards polysialic acid <i>in vitro.</i> The experimental design allowed us to study the impact of several factors that may influence polysialic acid degradation including pH, polymer size, and the relative ionic strength of the surrounding media. We report that short chains of polysialic acid (degree of polymerization, DP 3-8) were substrates of NEU3 and NEU4 at acidic pH, but not at neutral pH. No hNEU-catalyzed hydrolysis of longer polymers (DP 10-20) was detected. These findings suggest a neuraminidase-independent mechanism for polysialic acid turnover such as internalization and degradation in endosomes and lysosomes.