Recent advances in biocatalytic derivatization of L-tyrosine

Establishing an Artificial Pathway for the Biosynthesis of Octopamine and Synephrine

In this study, we designed an artificial pathway composed of tyramine β-hydroxylase (TBH) and phenylethanolamine N-methyltransferase (PNMT) for the biosynthesis of both octopamine and synephrine. As most TBH and PNMT originate from eukaryotic animals and plants, the heterologous expression and identification of functional TBH and PNMT are critical for establishing the pathway in mode microorganisms like Escherichia coli. Here, three TBHs were evaluated, and only TBH from Drosophila melanogaster was successfully expressed in the soluble form in E. coli. Its expression was promoted by evaluating the effects of different expression strategies. The specific enzyme activity of TBH was optimized up to 229.50 U·g-1, and the first step in the biosynthetic pathway was successfully established and converted tyramine to synthesize 0.10 g/L of octopamine. Furthermore, the second step to produce synephrine from octopamine was developed by screening PNMT, enhancing enzyme activity, and optimizing reaction conditions, with a maximum synephrine production of 2.02 g/L. Finally, based on the optimization of the reaction conditions for each individual reaction, the one-pot cascade reaction for synthesizing synephrine from tyramine was constructed by combining the TBH and PNMT. The synthetic synephrine reached 30.05 mg/L with tyramine as substrate in the two-step enzyme cascade system. With further optimization and amplification, the titers of octopamine and synephrine were increased to 0.45 and 0.20 g/L, respectively, with tyramine as substrate. This work was the first achievement of the biosynthesis of octopamine and synephrine to date.

Au@Ag nanoparticles: an analytical tool to study the effect of tyrosine on dopamine levels

The neurotransmitter dopamine (DA) plays important roles in the human body, including regulatory functions, movement, memory and motivational control. The direct intake of DA is impossible as it cannot cross the blood-brain barrier (BBB) efficiently. Notably, l-tyrosine works as a precursor of DA in the human brain. Herein, we report an analytical method that strongly supports the hypothesis that the intake of tyrosine (Tyr)-rich food enhances DA levels. For this analysis, citrate-coated gold-core silver-shell nanoparticles (Au@Ag NPs) were synthesized. The interaction of DA with the Au@Ag NPs was investigated using multiple spectroscopic techniques, and different thermodynamic parameters were evaluated to assign the binding mechanism. Real sample analysis with Tyr-rich food was also conducted to study the effect of Tyr on DA levels. Analytical studies were performed to verify the outcomes of the present work. The limit of detection of the Au@Ag NPs-DA system for Tyr was found to be 1.64 mM. This study can contribute to development in the fields of medicine and pharmaceuticals, particularly in regard to neuromedicine. One of the major advantages of this investigation is that it will fuel research interest in the supplementation of neurotransmitters and help categorize Tyr as a dietary precursor of dopamine.

Integrated metabolomic and transcriptomic analysis reveals the regulatory mechanisms of flavonoid and alkaloid biosynthesis in the new and old leaves of Murraya tetramera Huang

BACKGROUND

Murraya tetramera Huang is a traditional Chinese woody medicine. Its leaves contain flavonoids, alkaloids, and other active compounds, which have anti-inflammatory and analgesic effects, as well as hypoglycemic and lipid-lowering effects, and anti-tumor effects. There are significant differences in the content of flavonoids and alkaloids in leaves during different growth cycles, but the synthesis mechanism is still unclear.

RESULTS

In April 2021, new leaves (one month old) and old leaves (one and a half years old) of M. tetramera were used as experimental materials to systematically analyze the changes in differentially expressed genes (DEGs) and differentially accumulated metabolites (DAMs) with transcriptomics and metabolomics technology. This was done to identify the signaling pathways of flavonoid and alkaloid synthesis. The results showed that the contents of total alkaloids and flavonoids in old leaves were significantly higher than those in new leaves. Thirteen flavonoid compounds, three isoflavone compounds, and nineteen alkaloid compounds were identified, and 125 and 48 DEGs related to flavonoid and alkaloid synthesis were found, respectively. By constructing the KEGG (Kyoto Encyclopedia of Genes and Genomes) network of DEGs and DAMs, it was shown that the molecular mechanism of flavonoid biosynthesis in M. tetramera mainly focuses on the "flavonoid biosynthetic pathway" and the "flavonoid and flavonol biosynthetic pathway". Among them, p-Coumaryl alcohol, Sinapyl alcohol, Phloretin, and Isoquercitrin were significantly accumulated in old leaves, the up-regulated expression of CCR (cinnamoyl-CoA reductase) might promote the accumulation of p-Coumaryl alcohol, upregulation of F5H (ferulate-5-hydroxylase) might promote Sinapyl alcohol accumulation. Alkaloids, including indole alkaloids, pyridine alkaloids, imidazole alkaloids, and quinoline alkaloids, were significantly accumulated in old leaves, and a total of 29 genes were associated with these substances.

CONCLUSIONS

These data are helpful to better understand the biosynthesis of flavonoids and alkaloids in M. tetramera and provide a scientific basis for the development of medicinal components in M. tetramera.

Adsorption and Recognition Property of Tyrosine Molecularly Imprinted Polymer Prepared via Electron Beam Irradiation

To realize the selective separation of L-tyrosine (L-Tyr) and avoid the drawbacks of traditional thermal polymerization, electron beam irradiation polymerization was developed for the fabrication of L-Tyr molecularly imprinted polymers (MIPs). Firstly, L-Tyr MIPs were prepared with methacrylic acid and ethylene glycol dimethacrylate and without an initiator. Then, the influence of absorbed dosage and temperature on the adsorption capacity of L-Tyr, as well as the thermodynamic behavior, were investigated. The maximum adsorption capacity of 10.96 mg/g for MIPs was obtained with an irradiation dosage of 340 kGy under 15 °C, and the ΔH0 and ΔS0 of the adsorption process are -99.79 kJ/mol and -0.31 kJ/mol·K, respectively. In addition, the effect of adsorption time on adsorption performance was evaluated under different initial concentrations, and the kinetic behavior was fitted with four different models. Finally, the recognition property of the obtained MIPs was investigated with L-Tyr and two analogues. The obtained MIPs have an imprinting factor of 5.1 and relatively high selective coefficients of 3.9 and 3.5 against L-tryptophan and L-phenylalanine, respectively. This work not only provided an L-Tyr MIP with high adsorption capacity and selectivity but also provided an effective and clean method for the synthesis of MIPs.

Solid-state fermentation improves the quality of chrysanthemum waste as an alternative feed ingredient

Chrysanthemum waste (CW) is an agricultural and industrial by-product produced during chrysanthemum harvesting, drying, preservation, and deep processing. Although it is nutritious, most CW is discarded, wasting resources and contributing to serious environmental problems. This work explored a solid-state fermentation (SSF) strategy to improve CW quality for use as an alternative feed ingredient. Orthogonal experiment showed that the optimal conditions for fermented chrysanthemum waste (FCW) were: CW to cornmeal mass ratio of 9:1, Pediococcus cellaris + Candida tropicalis + Bacillus amyloliquefaciens proportions of 2:2:1, inoculation amount of 6%, and fermentation time of 10 d. Compared with the control group, FCW significantly increased the contents of crude protein, ether extract, crude fiber, acid detergent fiber, neutral detergent fiber, ash, calcium, phosphorus, and total flavonoids (p < 0.01), and significantly decreased pH and saponin content (p < 0.01). SSF improved the free and hydrolyzed amino acid profiles of FCW, increased the content of flavor amino acids, and improved the amino acid composition of FCW protein. Overall, SSF improved CW nutritional quality. FCW shows potential use as a feed ingredient, and SSF helps reduce the waste of chrysanthemum processing.

Effect of β - hydroxy - γ -aminophosphonate (β - HPC) on the hydrolytic activity of Nocardia brasiliensis as determined by FT-IR spectrometry

The use of immunomodulatory and metabolic modulating drugs has been considered a better strategy to improve the efficacy of conventional treatments against pathogens and metabolic diseases. L-carnitine is relevant in fatty acid metabolism and energy production by β-oxidation, but it also has a beneficial therapeutic immunomodulatory effect. The β-hydroxy-γ-aminophosphonate (β-HPC) was developed, synthesized and studied in different pathologies as a more soluble and stable analog than L-carnitine, which has been studied in bacterial physiology and metabolism; therefore, we set out to investigate the direct effect of β-HPC on the metabolism of N. brasiliensis, which causes actinomycetoma in Mexico and is underdiagnosed. To analyze the effect of β-HPC on the metabolic capacity of the bacterium for the hydrolysis of substrate casein, L-tyrosine, egg yolk, and tween 80, Fourier transform infrared spectroscopy (FT-IR) was employed. It was found that β-HPC increases the metabolic activity of N. brasiliensis associated with increased growth and increased hydrolysis of the substrates tested. By the effect of β-HPC, it was observed that, in the hydrolysis of L-tyrosine, the aromatic ring and functional groups were degraded. At 1515 cm^-1, any distinctive signal or peak for this amino acid was missing, almost disappearing at 839, 720, 647, and 550 cm^-1. In casein, hydrolysis is enhanced in the substrate, which is evident by the presence of NH, OH, amide, and CO. In casein, hydrolysis is enhanced in the substrate, which is evident by the presence of NH, OH, amide, COO, and P = O signals, characteristic of amino acids, in addition to the increase of the amide I and II bands. In Tween 80 the H-C = and C = C signals disappear and the ether signals are concentrated, it was distinguished by the intense band at 1100 cm^-1. Egg yolk showed a large accumulation of phosphate groups at 1071 cm^-1, where phosvitin is located. FT-IR has served to demonstrate that β-HPC is a hydrolysis enhancer. Furthermore, by obtaining the spectrum of N. brasiliensis, we intend to use it as a quick comparison tool with other spectra related to actinobacteria. Eventually, FT-IR may serve as a species identification option.

Recent advances in (chemo)enzymatic cascades for upgrading bio-based resources

Developing (chemo)enzymatic cascades is very attractive for green synthesis, because they streamline multistep synthetic processes. In this Feature Article, we have summarized the recent advances in in vitro or whole-cell cascade reactions with a focus on the use of renewable bio-based resources as starting materials. This includes the synthesis of rare sugars (such as ketoses, L-ribulose, D-tagatose, myo-inositol or aminosugars) from readily available carbohydrate sources (cellulose, hemi-cellulose, starch), in vitro enzyme pathways to convert glucose to various biochemicals, cascades to convert 5-hydroxymethylfurfural and furfural obtained from lignin or xylose into novel precursors for polymer synthesis, the syntheses of phenolic compounds, cascade syntheses of aliphatic and highly reduced chemicals from plant oils and fatty acids, upgrading of glycerol or ethanol as well as cascades to transform natural L-amino acids into high-value (chiral) compounds. In several examples these processes have demonstrated their efficiency with respect to high space-time yields and low E-factors enabling mature green chemistry processes. Also, the strengths and limitations are discussed and an outlook is provided for improving the existing and developing new cascades.

Cost-Effective Production of L-DOPA by Tyrosinase-Immobilized Polyhydroxyalkanoate Nanogranules in Engineered Halomonas bluephagenesis TD01

3,4-dihydroxyphenyl-L-alanine (L-DOPA) is a preferred drug for Parkinson's disease, with an increasing demand worldwide that mainly relies on costly and environmentally problematic chemical synthesis. Yet, biological L-DOPA production is unfeasible at the industrial scale due to its low L-DOPA yield and high production cost. In this study, low-cost Halomonas bluephagenesis TD01 was engineered to produce tyrosinase TyrVs-immobilized polyhydroxyalkanoate (PHA) nanogranules in vivo, with the improved PHA content and increased immobilization efficiency of TyrVs accounting for 6.85% on the surface of PHA. A higher L-DOPA-forming monophenolase activity of 518.87 U/g PHA granules and an L-DOPA concentration of 974.36 mg/L in 3 h catalysis were achieved, compared to those of E. coli. Together with the result of L-DOPA production directly by cell lysates containing PHA-TyrVs nanogranules, our study demonstrated the robust and cost-effective production of L-DOPA by H. bluephagenesis, further contributing to its low-cost industrial production based on next-generation industrial biotechnology (NGIB).