Commonalities Between ARDS, Pulmonary Fibrosis and COVID-19: The Potential of Autotaxin as a Therapeutic Target

Severe COVID-19 is characterized by acute respiratory distress syndrome (ARDS)-like hyperinflammation and endothelial dysfunction, that can lead to respiratory and multi organ failure and death. Interstitial lung diseases (ILD) and pulmonary fibrosis confer an increased risk for severe disease, while a subset of COVID-19-related ARDS surviving patients will develop a fibroproliferative response that can persist post hospitalization. Autotaxin (ATX) is a secreted lysophospholipase D, largely responsible for the extracellular production of lysophosphatidic acid (LPA), a pleiotropic signaling lysophospholipid with multiple effects in pulmonary and immune cells. In this review, we discuss the similarities of COVID-19, ARDS and ILDs, and suggest ATX as a possible pathologic link and a potential common therapeutic target.

Highly Efficient Extracellular Production of Recombinant Streptomyces PMF Phospholipase D in Escherichia coli

To achieve efficient bio-production of phospholipase D (PLD), PLDs from different organisms were expressed in E.coli. An efficient secretory expression system was thereby developed for PLD. First, PLDs from Streptomyces PMF and Streptomyces racemochromogenes were separately over-expressed in E.coli to compare their transphosphatidylation activity based on the synthesis of phosphatidylserine (PS), and PLDPMF was determined to have higher activity. To further improve PLDPMF synthesis, a secretory expression system suitable for PLDPMF was constructed and optimized with different signal peptides. The highest secretory efficiency was observed when the PLD * (PLDPMF with the native signal peptide Nat removed) was expressed fused with the fusion signal peptide PelB-Nat in E. coli. The fermentation conditions were also investigated to increase the production of recombinant PLD and 10.5 U/mL PLD was ultimately obtained under the optimized conditions. For the application of recombinant PLD to PS synthesis, the PLD properties were characterized and 30.2 g/L of PS was produced after 24 h of bioconversion when 50 g/L phosphatidylcholine (PC) was added.

Investigation of Optimal Conditions for Production, Characterization, and Immobilization of Fructosyltransferase and β-Fructofuranosidase by Filamentous Fungi

This work's objective was the extracellular production, partial characterization, and immobilization of the enzymes fructosyltransferase (Ftase) and β-fructofuranosidadase (Ffase) by filamentous fungi. Aspergillus niger ATCC 9642 and Penicillium brasilianum were evaluated for the production of fructosyltransferase (Ftase) and β-fructofuranosidadase (FASE) enzymes. The A. niger presented the highest activity of FTase (24.86 µmol/min.mL) and FFase (28.68 µmol/min.mL) in medium composed of 20% sucrose, 0.5% yeast extract, 1% NaNO3, 0.05% MgSO4.7 H2O, 0.25% KH2PO4, 0.5% NH4Cl and 0.25% NaCl inoculated using 5x107spores/mL and incubated at 25°C, pH 5.5, 150 rpm for 48 h. Presenting optimum pH and temperature of 2.39 and 60°C. Thermal stability has shown that the enzyme FFase is more thermally stable when compared to FTase. Stability against different pHs showed similar behavior for FTase and FFase; the optimum pH being between 2.0 and 3.0. FTase and FFase showed storage stability in freezing and refrigeration temperature for approximately 400 h. The kinetic parameters, Km and Vmax, for the sucrose substrate were 24.60mM and 104.16 μmol/min.mL for FTase and 3.91mM and 20.24 μmol/min.mL for FFase. The immobilization process displayed a yield of 6744.66% for FFase and 3928.90% for FTase, with enzymatic activities of 364.79 U/g and 220.34 U/g, and 4 and 3 times reuse, respectively.