A continuous spectrophotometric assay that distinguishes between phospholipase A1 and A2 activities

Phospholipase Family Enzymes in Lung Cancer: Looking for Novel Therapeutic Approaches

Lung cancer (LC) is the second most common neoplasm in men and the third most common in women. In the last decade, LC therapies have undergone significant improvements with the advent of immunotherapy. However, the effectiveness of the available treatments remains insufficient due to the presence of therapy-resistant cancer cells. For decades, chemotherapy and radiotherapy have dominated the treatment strategy for LC; however, relapses occur rapidly and result in poor survival. Malignant lung tumors are classified as either small- or non-small-cell lung carcinoma (SCLC and NSCLC). Despite improvements in the treatment of LC in recent decades, the benefits of surgery, radiotherapy, and chemotherapy are limited, although they have improved the prognosis of LC despite the persistent low survival rate due to distant metastasis in the late stage. The identification of novel prognostic molecular markers is crucial to understand the underlying mechanisms of LC initiation and progression. The potential role of phosphatidylinositol in tumor growth and the metastatic process has recently been suggested by some researchers. Phosphatidylinositols are lipid molecules and key players in the inositol signaling pathway that have a pivotal role in cell cycle regulation, proliferation, differentiation, membrane trafficking, and gene expression. In this review, we discuss the current understanding of phosphoinositide-specific phospholipase enzymes and their emerging roles in LC.

Membrane plasticity induced by myo-inositol derived archaeal lipids: chemical synthesis and biophysical characterization

Archaeal membrane lipids have specific structures that allow Archaea to withstand extreme conditions of temperature and pressure. In order to understand the molecular parameters that govern such resistance, the synthesis of 1,2-di-O-phytanyl-sn-glycero-3-phosphoinositol (DoPhPI), an archaeal lipid derived from myo-inositol, is reported. Benzyl protected myo-inositol was first prepared and then transformed to phosphodiester derivatives using a phosphoramidite based-coupling reaction with archaeol. Aqueous dispersions of DoPhPI alone or mixed with DoPhPC can be extruded and form small unilamellar vesicles, as detected by DLS. Neutron, SAXS, and solid-state NMR demonstrated that the water dispersions could form a lamellar phase at room temperature that then evolves into cubic and hexagonal phases with increasing temperature. Phytanyl chains were also found to impart remarkable and nearly constant dynamics to the bilayer over wide temperature ranges. All these new properties of archaeal lipids are proposed as providers of plasticity and thus means for the archaeal membrane to resist extreme conditions.

In situ monitoring of galactolipid digestion by infrared spectroscopy in both model micelles and spinach chloroplasts

Galactolipids are the main lipids from plant photosynthetic membranes and they can be digested by pancreatic lipase related protein 2 (PLRP2), an enzyme found in the pancreatic secretion in many animal species. Here, we used transmission Fourier-transform infrared spectroscopy (FTIR) to monitor continuously the hydrolysis of galactolipids by PLRP2, in situ and in real time. The method was first developed with a model substrate, a synthetic monogalactosyl diacylglycerol with 8-carbon acyl chains (C8-MGDG), in the form of mixed micelles with a bile salt, sodium taurodeoxycholate (NaTDC). The concentrations of the residual substrate and reaction products (monogalactosylmonoglyceride, MGMG; monogalactosylglycerol, MGG; octanoic acid) were estimated from the carbonyl and carboxylate vibration bands after calibration with reference standards. The results were confirmed by thin layer chromatography analysis (TLC) and specific staining of galactosylated compounds with thymol and sulfuric acid. The method was then applied to the lipolysis of more complex substrates, a natural extract of MGDG with long acyl chains, micellized with NaTDC, and intact chloroplasts isolated from spinach leaves. After a calibration performed with α-linolenic acid, the main fatty acid (FA) found in plant galactolipids, FTIR allowed quantitative measurement of chloroplast lipolysis by PLRP2. A full release of FA from membrane galactolipids was observed, that was not dependent on the presence of bile salts. Nevertheless, the evolution of amide vibration band in FTIR spectra suggested the interaction of membrane proteins with NaTDC and lipolysis products.

Biochemical characterization of an alkaline and detergent-stable Lipase from Fusarium annulatum Bugnicourt strain CBS associated with olive tree dieback

This work describes a novel extracellular lipolytic carboxylester hydrolase named FAL, with lipase and phospholipase A1 (PLA1) activity, from a newly isolated filamentous fungus Ascomycota CBS strain, identified as Fusarium annulatum Bunigcourt. FAL was purified to about 62-fold using ammonium sulphate precipitation, Superdex® 200 Increase gel filtration and Q-Sepharose Fast Flow columns, with a total yield of 21%. The specific activity of FAL was found to be 3500 U/mg at pH 9 and 40°C and 5000 U/mg at pH 11 and 45°C, on emulsions of triocanoin and egg yolk phosphatidylcholine, respectively. SDS-PAGE and zymography analysis estimated the molecular weight of FAL to be 33 kDa. FAL was shown to be a PLA1 with a regioselectivity to the sn-1 position of surface-coated phospholipids esterified with α-eleostearic acid. FAL is a serine enzyme since its activity on triglycerides and phospholipids was completely inhibited by the lipase inhibitor Orlistat (40 μM). Interestingly, compared to Fusarium graminearum lipase (GZEL) and the Thermomyces lanuginosus lipase (Lipolase®), this novel fungal (phospho)lipase showed extreme tolerance to the presence of non-polar organic solvents, non-ionic and anionic surfactants, and oxidants, in addition to significant compatibility and stability with some available laundry detergents. The analysis of washing performance showed that it has the capability to efficiently eliminate oil-stains. Overall, FAL could be an ideal choice for application in detergents.

Quantitative monitoring of galactolipid hydrolysis by pancreatic lipase-related protein 2 using thin layer chromatography and thymol-sulfuric acid derivatization

Galactolipids are the most abundant lipids on earth where they are mainly found in photosynthetic membranes of plant, algae, and cyanobacteria. Pancreatic lipase-related protein 2 (PLRP2) is an enzyme with galactolipase activity allowing mammals, especially herbivores, to digest this important source of fatty acids. We present a method for the quantitative analysis of galactolipids and galactosylated products resulting from their digestion by guinea pig PLRP2 (GPLRP2), using thin-layer-chromatography (TLC), thymol-sulfuric acid as derivatization reagent and scanning densitometry for detection. Thymol-sulfuric acid reagent has been used for the colorimetric detection of carbohydrates. It is shown here that the derivatization of galactosyl group from galactolipids by this reagent is not affected by the bound acyl glycerol, acyl chains length and number of galactose residues in the polar head. This allowed quantifying simultaneously the initial substrate and all galactosylated products generated upon the hydrolysis of monogalactosyl di-octanoylglycerol (C8-MGDG) by GPLRP2 using a single calibration with C8-MGDG as reference standard. The reaction products, monogalactosyl monooctanoyl glycerol (C8-MGMG) and monogalactosyl glycerol (MGG), were identified and quantified, MGG being recovered from the aqueous phase and analyzed by a separate TLC analysis. This method is therefore suitable to quantify the products resulting from the release of both fatty acids present in MGDG and thereby shows that PLRP2 can contribute to the complete digestion of galactolipids and further intestinal absorption of their fatty acids.

A Role of Newly Found Auxiliary Site in Phospholipase A1 from Thai Banded Tiger Wasp (Vespa affinis) in Its Enzymatic Enhancement: In Silico Homology Modeling and Molecular Dynamics Insights

Phospholipase A₁ from Thai banded tiger wasp (Vespa affinis) venom also known as Ves a 1 plays an essential role in fatal vespid allergy. Ves a 1 becomes an important therapeutic target for toxin remedy. However, established Ves a 1 structure or a mechanism of Ves a 1 function were not well documented. This circumstance has prevented efficient design of a potential phospholipase A₁ inhibitor. In our study, we successfully recruited homology modeling and molecular dynamic (MD) simulation to model Ves a 1 three-dimensional structure. The Ves a 1 structure along with dynamic behaviors were visualized and explained. In addition, we performed molecular docking of Ves a 1 with 1,2-Dimyristoyl-sn-glycero-3-phosphorylcholine (DMPC) lipid to assess a possible lipid binding site. Interestingly, molecular docking predicted another lipid binding region apart from its corresponding catalytic site, suggesting an auxiliary role of the alternative site at the Ves a 1 surface. The new molecular mechanism related to the surface lipid binding site (auxiliary site) provided better understanding of how phospholipase A₁ structure facilitates its enzymatic function. This auxiliary site, conserved among Hymenoptera species as well as some mammalian lipases, could be a guide for interaction-based design of a novel phospholipase A₁ inhibitor.

Vegetable lecithins: A review of their compositional diversity, impact on lipid metabolism and potential in cardiometabolic disease prevention

Vegetable lecithins, widely used in the food industry as emulsifiers, are a mixture of naturally occurring lipids containing more than 50% of phospholipids (PL). PL exert numerous important physiological effects. Their amphiphilic nature notably enables them to stabilise endogenous lipid droplets, conferring them an important role in lipoprotein transport, functionality and metabolism. In addition, beneficial effects of dietary lecithin on metabolic disorders have been reported since the 1990s. This review attempts to summarize the effects of various vegetable lecithins on lipid and lipoprotein metabolism, as well as their potential application in the treatment of dyslipidemia associated with metabolic disorders. Despite controversial data concerning the impact of vegetable lecithins on lipid digestion and intestinal absorption, the beneficial effect of lecithin supplementation on plasma and hepatic lipoprotein and cholesterol levels is unequivocal. This is especially true in hyperlipidemic patients. Furthermore, the immense compositional diversity of vegetable lecithins endows them with a vast range of biochemical and biological properties, which remain to be explored in detail. Data on the effects of vegetable lecithins alternative to soybean, both as supplements and as ingredients in different foods, is undoubtedly lacking. Given the exponential demand for vegetable products alternative to those of animal origin, it is of primordial importance that future research is undertaken in order to elucidate the mechanisms by which individual fatty acids and PL from various vegetable lecithins modulate lipid metabolism. The extent to which they may influence parameters associated with metabolic disorders, such as intestinal integrity, low-grade inflammation and gut microbiota must also be assessed.

A Continuous and Sensitive Spectrophotometric Assay for Lipase and Phospholipase A Activities Using α-Eleostearic Acid-Containing Substrates

To date, several sensitive methods, based on radiolabeled elements or sterically hindered fluorochrome groups, are usually employed to screen lipase and phospholipase A (PLA) activities. Here, a new ultraviolet spectrophotometric assay for lipase or PLA was developed using natural triglycerides or synthetic glycerophosphatidylcholines containing α-eleostearic acid (9Z, 11E, 13E-octadecatrienoic acid) purified from Aleurites fordii seed oil. The conjugated triene present in α-eleostearic acid constitutes an intrinsic chromophore and consequently confers strong UV absorption properties of this free fatty acid as well as of lipid substrates harboring it. The substrate was coated into the wells of a microplate, and the lipolytic activities were measured by the absorbance increase at 272 nm due to the transition of α-eleostearic acid moiety from the adsorbed to the soluble state. This continuous assay is compatible with a high-throughput screening method and can be applied specifically to the screening of new potential lipase, PLA₁ and PLA₂ inhibitors.

IR spectroscopy analysis of pancreatic lipase-related protein 2 interaction with phospholipids: 3. Monitoring DPPC lipolysis in mixed micelles

Usual methods for the continuous assay of lipolytic enzyme activities are mainly based on the titration of free fatty acids, surface pressure monitoring or spectrophotometry using substrates labeled with specific probes. These approaches only give a partial information on the chemistry of the lipolysis reaction and additional end-point analyses are often required to quantify both residual substrate and lipolysis products. We used transmission infrared (IR) spectroscopy to monitor simultaneously the hydrolysis of phospholipids by guinea pig pancreatic lipase-related protein 2 (GPLRP2) and the release of lipolysis products. The substrate (DPPC, 1,2-Dipalmitoyl phosphatidylcholine) was mixed with sodium taurodeoxycholate (NaTDC) to form mixed micelles in D₂O buffer at pD 6 and 8. After hydrogen/deuterium exchange, DPPC hydrolysis by GPLRP2 (100nM) was monitored at 35°C in a liquid cell by recording IR spectra and time-course variations in the CO stretching region. These changes were correlated to variations in the concentrations of DPPC, lysophospholipids (lysoPC) and palmitic acid (Pam) using calibration curves established with these compounds individually mixed with NaTDC. We were thus able to quantify each compound and its time-course variations during the phospholipolysis reaction and to estimate the enzyme activity. To validate the IR analysis, variations in residual DPPC, lysoPC and Pam were also quantified by thin-layer chromatography coupled to densitometry and similar hydrolysis profiles were obtained using both methods. IR spectroscopy can therefore be used to monitor the enzymatic hydrolysis of phospholipids and obtain simultaneously chemical and physicochemical information on substrate and all reaction products (H-bonding, hydration, acyl chain mobility).

Screening of phospholipase A activity and its production by new actinomycete strains cultivated by solid-state fermentation

Novel microbial phospholipases A (PLAs) can be found in actinomycetes which have been poorly explored as producers of this activity. To investigate microbial PLA production, efficient methods are necessary such as high-throughput screening (HTS) assays for direct search of PLAs in microbial cultures and cultivation conditions to promote this activity. About 200 strains isolated with selected media for actinomycetes and mostly belonging to Streptomyces (73%) and Micromonospora (10%) genus were first screened on agar-plates containing the fluorophore rhodamine 6G and egg yolk phosphatidylcholine (PC) to detect strains producing phospholipase activity. Then, a colorimetric HTS assay for general PLA activity detection (cHTS-PLA) using enriched PC (≈60%) as substrate and cresol red as indicator was developed and applied; this cHTS-PLA assay was validated with known PLAs. For the first time, actinomycete strains were cultivated by solid-state fermentation (SSF) using PC as inductor and sugar-cane bagasse as support to produce high PLA activity (from 207 to 2,591 mU/g of support). Phospholipase activity of the enzymatic extracts from SSF was determined using the implemented cHTS-PLA assay and the PC hydrolysis products obtained, were analyzed by TLC showing the presence of lyso-PC. Three actinomycete strains of the Streptomyces genus that stood out for high accumulation of lyso-PC, were selected and analyzed with the specific substrate 1,2-α-eleostearoyl-sn-glycero-3-phosphocholine (EEPC) in order to confirm the presence of PLA activity in their enzymatic extracts. Overall, the results obtained pave the way toward the HTS of PLA activity in crude microbial enzymatic extracts at a larger scale. The cHTS-PLA assay developed here can be also proposed as a routine assay for PLA activity determination during enzyme purification,directed evolution or mutagenesis approaches. In addition, the production of PLA activity by actinomycetes using SSF allow find and produce novel PLAs with potential applications in biotechnology.