Highly Efficient Chemoenzymatic Synthesis of l-Phosphinothricin from N-Phenylacetyl-d,l-phosphinothricin by a Robust Immobilized Amidase

Identification of efficient amine transaminase and applicability in dual transaminases cascade for synthesis of L-phosphinothricin

L-phosphinothricin (L-PPT) is the most popular broad-spectrum and highly effective herbicide. Transaminases (TAs) play a pivotal role in asymmetric synthesis of L-PPT, yet encounter the challenge of unfavorable reaction equilibrium. In this study, the novel dual transaminases cascade system (DTCS) was introduced to facilitate the synthesis of L-PPT. The specific amine transaminase BdATA, originating from Bradyrhizobium diazoefficiens ZJY088, was screened and identified. It exhibited remarkable activity, good stability, and required only 2.5 equivalents of isopropylamine to transform pyruvate effectively. By coupling BdATA with previously reported SeTA to construct the DTCS for pyruvate removal in situ, the L-PPT yield escalated from 37.37 % to 85.35 %. Three advantages of the DTCS were presented: the removal of pyruvate alleviated by-product inhibition, the use of isopropylamine reduced reliance on excess L-alanine, and no demand for expensive cofactors like NAD(P)H. It demonstrated an innovative idea for addressing the challenges associated with transaminase-mediated synthesis of L-PPT.

Heterologous expression of a deacetylase and its application in L-glufosinate preparation

With potent herbicidal activity, biocatalysis synthesis of L-glufosinate has drawn attention. In present research, NAP-Das2.3, a deacetylase capable of stereoselectively resolving N-acetyl-L-glufosinate to L-glufosinate mined from Arenimonas malthae, was heterologously expressed and characterized. In Escherichia coli, NAP-Das2.3 activity only reached 0.25 U/L due to the formation of inclusive bodies. Efficient soluble expression of NAP-Das2.3 was achieved in Pichia pastoris. In shake flask and 5 L bioreactor fermentation, NAP-Das2.3 activity by recombinant P. pastoris reached 107.39 U/L and 1287.52 U/L, respectively. The optimum temperature and pH for N-acetyl-glufosinate hydrolysis by NAP-Das2.3 were 45 °C and pH 8.0, respectively. The Km and Vmax of NAP-Das2.3 towards N-acetyl-glufosinate were 25.32 mM and 19.23 μmol mg-1 min-1, respectively. Within 90 min, 92.71% of L-enantiomer in 100 mM racemic N-acetyl-glufosinate was converted by NAP-Das2.3. L-glufosinate with high optical purity (e.e.P above 99.9%) was obtained. Therefore, the recombinant NAP-Das2.3 might be an alternative for L-glufosinate biosynthesis.

Comparing the enantioselective toxicity on cell cycle and apoptosis of DL-glufosinate and L-glufosinate to SH-SY5Y cells

Glufosinate (Glu), a broad-spectrum and highly effective non-selective herbicide, behaves in typical chiral features to target organisms. However, the information on the enantioselective toxicity of DL-Glu and L-Glu against non-target organisms is still limited especially at environmental concentrations. In this study, we investigated the potential mechanism accounting for the enantioselective cytotoxicity of Glu based on cell cycle and apoptosis. Results showed that DL-Glu and L-Glu had no suppression on cell viability at 10-5 M, however, SH-SY5Y cells were significantly arrested at G1/G0 phase after L-Glu exposure compared with DL-Glu. The apoptosis assay exhibited an increase in late apoptosis cells and a decrease in viable cells for DL-Glu and L-Glu treatment. The bioinformatics analysis demonstrated that alterations in transcription translation and signal transduction including "calcium signaling pathway", "Wnt signaling pathway", "FoxO signaling pathway" were the possible pathways responsible for Glu-induced enantioselectivity in cell cycle and apoptosis. Interestingly, the Gene Set Enrichment Analysis (GSEA) also revealed the probable association between DL-Glu exposure and degenerative diseases. These findings serve as a reminder that caution should be exercised not only when using pesticide racemates but also when promoting or applying single- or enriched-isomer pesticides.