Purification and biochemical characterization of phospholipase A2 from dromedary pancreas

Biochemical, Kinetic and Biological Properties of Group V Phospholipase A2 from Dromedary

Secretory group V phospholipase A2 (PLA₂-V) is known to be involved in inflammatory processes in cellular studies, nevertheless, the biochemical and the enzymatic characteristics of this important enzyme have been unclear yet. We reported, as a first step towards understanding the biochemical properties, catalytic characteristics, antimicrobial and cytotoxic effects of this PLA₂, the production of PLA₂-V from dromedary. The obtained DrPLA₂-V has an absolute requirement for Ca²⁺ and NaTDC for enzymatic activity with an optimum pH of 9 and temperature of 45 °C with phosphatidylethanolamine as a substrate. Kinetic parameters showed that K_cat/Km_app is 2.6 ± 0.02 mM⁻¹ s⁻¹. The enzyme was found to display potent Gram-positive bactericidal activity (with IC50 values of about 5 µg/mL) and antifungal activity (with IC50 values of about 25 µg/mL)in vitro. However, the purified enzyme did not display a cytotoxic effect against cancer cells.

Cytotoxic, Antioxidant, and Metabolic Enzyme Inhibitory Activities of Euphorbia cyparissias Extracts

Plants of the Euphorbia genus present a wide range of therapeutic applications. This study is aimed at investigating new antidigestive enzyme agents from Euphorbia cyparissias through inhibition of lipid and carbohydrate absorption, to evaluate their potential applications for the treatment of metabolic syndrome. Lipase, phospholipase, protease, α-amylase, β-glucosidase, and xanthine oxidase activities under treatment with aqueous and ethanolic extracts of Euphorbia cyparissias were observed to evaluate the inhibitory effect of these extracts, as well as their antioxidant and cytotoxic effects. Results showed that ethanolic and aqueous extracts exhibited important inhibitory activity in a concentration-related manner on digestive enzymes, which is more effective than the commercial drugs used as controls. Results also showed that, out of the two extracts tested, the ethanolic extract presented the most promising results in inhibiting the activities of all digestive enzymes used. Moreover, the two extracts displayed a higher reducing power than that of the positive control used. The obtained results, together with previous reports in the literature, strongly suggest that Euphorbia cyparissias extracts may be natural inhibitors of the digestive enzymes and thus a potential new drug for metabolic syndrome treatment.

Heterologous Expression and Functional Characterization of Sparidae Fish Digestive Phospholipase A2

In this study, we have produced for the first time a fish phospholipase (PLA₂) in heterologous system (E. coli). The Diplodus annularis PLA₂ (DaPLA₂) was then refolded from inclusion bodies and purified by Ni-affinity chromatography. We used the pH-stat method (with emulsified phosphatidylcholine as substrate) and the monomolecular film technique (using various glycerophospholipids substrates spread in the form of monomolecular films at the air-water interface) to access the biochemical and kinetic properties of the recombinant DaPLA₂. The DaPLA₂ was found to be active and stable at higher temperatures (37-50 °C) than expected. Interestingly, DaPLA₂ hydrolyzes efficiently both purified phosphatidylglycerol and phosphatidylethanolamine at 20 mN/m. These analytical results corroborate with the fact that the catalytic activity of DaPLA₂, measured with the pH-stat using egg yolk as substrate, is mainly due to the hydrolysis of the PE fraction present in egg yolk, whereas the phosphatidylglycerol is a hallmark substrate for the most secreted PLA₂-IB.

Functional and Structural Characterization of a Thermostable Phospholipase A2 from a Sparidae Fish (Diplodus annularis)

Novel phospholipase (PLA₂) genes from the Sparidae family were cloned. The sequenced PLA₂ revealed an identity with pancreatic PLA₂ group IB. To better understand the structure/function relationships of these enzymes and their evolution, the Diplodus annularis PLA₂ (DaPLA₂) was overexpressed in E. coli. The refolded enzyme was purified by Ni-affinity chromatography and has a molecular mass of 15 kDa as determined by MALDI-TOF spectrometry. Interestingly, unlike the pancreatic type, the DaPLA₂ was active and stable at higher temperatures, which suggests its great potential in biotechnological applications. The 3D structure of DaPLA₂ was constructed to gain insights into the functional properties of sparidae PLA₂. Molecular docking and dynamic simulations were performed to explain the higher thermal stability and the substrate specificity of DaPLA₂. Using the monolayer technique, the purified DaPLA₂ was found to be active on various phospholipids ranging from 10 to 20 mN·m^-1, which explained the absence of the hemolytic activity for DaPLA₂.

Kinetic characterization, optimum conditions for catalysis and substrate preference of secretory phospholipase A2 from Glycine max in model membrane systems

Two secretory phospholipase A2 (sPLA2s) from Glycine max, GmsPLA2-IXA-1 and GmsPLA2-XIB-2, have been purified as recombinant proteins and the activity was evaluated in order to obtain the optimum conditions for catalysis using mixed micelles and lipid monolayers as substrate. Both sPLA2s showed a maximum enzyme activity at pH 7 and a requirement of Ca(2+) in the micromolar range. These parameters were similar to those found for animal sPLA2s but a surprising optimum temperature for catalysis at 60 °C was observed. The effect of negative interfacial charges on the hydrolysis of organized substrates was evaluated through initial rate measurements using short chain phospholipids with different head groups. The enzymes showed subtle differences in the specificity for phospholipids with different head groups (DLPC, DLPG, DLPE, DLPA) in presence or absence of NaCl. Both recombinant enzymes showed lower activity toward anionic phospholipids and a preference for the zwitterionic ones. The values of the apparent kinetic parameters (Vmax and KM) demonstrated that these enzymes have more affinity for phosphatidylcholine compared with phosphatidylglycerol, in contrast with the results observed for pancreatic sPLA2. A hopping mode of catalysis was proposed for the action of these sPLA2 on mixed phospholipid/triton micelles. On the other hand, Langmuir-monolayers assays indicated an optimum lateral surface pressure for activity in between 13 and 16 mN/m for both recombinant enzymes.

Anti-bactericidal properties of stingray Dasyatis pastinaca groups V, IIA, and IB phospholipases A2: a comparative study

Group IIA secreted phospholipase A2 (group IIA sPLA2) is known to display potent Gram-positive bactericidal activity in vitro and in vivo. We have analyzed the bactericidal activity of the full set of native stingray and dromedary groups V, IIA, and IB sPLA2s on several Gram-positive and Gram-negative strains. The rank order potency among both marine and mammal sPLA2s against Gram-positive bacteria is group IIA > V > IB, whereas Gram-negative bacteria exhibited a much higher resistance. There is a synergic action of the sPLA2 with lysozyme when added to the bacteria culture prior to sPLA2.The bactericidal efficiency of groups V and IIA sPLA2s was shown to be dependent upon the presence of calcium ions and to a less extent Mg(2+) ions and then a correlation could be made to its hydrolytic activity of membrane phospholipids. Importantly, we showed that stingray and dromedary groups V, IIA, and IB sPLA2s present no cytotoxicity after their incubation with MDA-MB-231cells. stingray groups V and IIA sPLA2s, like mammal ones, may be considered as future therapeutic agents against bacterial infections.

Proteolytic cleavage of stingray phospholipase A2: isolation and biochemical characterization of an active N-terminal form

Background

Mammalian GIB-PLA2 are well characterized. In contrast, much less is known about aquatic ones. The aquatic world contains a wide variety of living species and, hence represents a great potential for discovering new lipolytic enzymes. The aim of this study was to check some biochemical and structural properties of a marine stingray phospholipase A2 (SPLA2).

Results

The effect of some proteolytic enzymes on SPLA2 was checked. Chymotrypsin and trypsin were able to hydrolyze SPLA2 in different ways. In both cases, only N-terminal fragments were accumulated during the hydrolysis, whereas no C-terminal fragment was obtained in either case. Tryptic and chymotryptic attack generated 13 kDa and 12 kDa forms of SPLA2, respectively. Interestingly, the SPLA2 13 kDa form was inactive, whereas the SPLA2 12 kDa form conserved almost its full phospholipase activity. In the absence of bile slats both native and 12kDa SPLA2 failed to catalyse the hydrolysis of PC emulsion. When bile salts were pre-incubated with the substrate, the native kinetic protein remained linear for more than 25 min, whereas the 12 kDa form activity was found to decrease rapidly. Furthermore, The SPLA2 activity was dependent on Ca²⁺; other cations (Mg²⁺, Mn²⁺, Cd²⁺ and Zn²⁺) reduced the enzymatic activity notably, suggesting that the arrangement of the catalytic site presents an exclusive structure for Ca²⁺.

Conclusions

Although marine and mammal pancreatic PLA2 share a high amino acid sequence homology, polyclonal antibodies directed against SPLA2 failed to recognize mammal PLA2 like the dromedary pancreatic one. Further investigations are needed to identify key residues involved in substrate recognition responsible for biochemical differences between the 2 classes of phospholipases.

Purification and biochemical characterization of pancreatic phospholipase A2 from the common stingray Dasyatis pastinaca

BACKGROUND

Mammalian sPLA2-IB are well characterized. In contrast, much less is known about aquatic ones. The aquatic world contains a wide variety of living species and, hence represents a great potential for discovering new lipolytic enzymes.

RESULTS

A marine stingray phospholipase A2 (SPLA2) was purified from delipidated pancreas. Purified SPLA2, which is not glycosylated protein, was found to be monomeric protein with a molecular mass of 14 kDa. A specific activity of 750 U/mg for purified SPLA2 was measured at optimal conditions (pH 8.5 and 40 °C) in the presence of 4 mM NaTDC and 8 mM CaCl2 using PC as substrate. The sequence of the first twenty first amino-acid residues at the N-terminal extremity of SPLA2 was determined and shows a close similarity with known mammal and bird pancreatic secreted phospholipases A2. SPLA2 stability in the presence of organic solvents, as well as in acidic and alkaline pH and at high temperature makes it a good candidate for its application in food industry.

CONCLUSIONS

SPLA2 has several advantageous features for industrial applications. Stability of SPLA2 in the presence of organic solvents, and its tolerance to high temperatures, basic and acidic pH, makes it a good candidate for application in food industry to treat phospholipid-rich industrial effluents, or to synthesize useful chemical compounds.

Purification and biochemical characterization of a secreted group IIA chicken intestinal phospholipase A₂

Background

Secretory phospholipase A2 group IIA (IIA PLA2) is a protein shown to be highly expressed in the intestine of mammals. However, no study was reported in birds.

Results

Chicken intestinal group IIA phospholipase A₂ (ChPLA₂-IIA) was obtained after an acidic treatment (pH.3.0), precipitation by ammonium sulphate, followed by sequential column chromatographies on Sephadex G-50 and mono-S ion exchanger. The enzyme was found to be a monomeric protein with a molecular mass of around 14 kDa. The purified enzyme showed a substrate preference for phosphatidylethanolamine and phosphatidylglycerol, and didn't hydrolyse phosphatidylcholine. Under optimal assay conditions, in the presence of 10 mM NaTDC and 10 mM CaCl_2, a specific activity of 160 U.mg^-1 for purified ChPLA₂-IIA was measured using egg yolk as substrate. The fifteen NH2-terminal amino acid residues of ChPLA₂-IIA were sequenced and showed a close homology with known intestinal secreted phospholipases A₂. The gene encoding the mature ChPLA₂-IIA was cloned and sequenced. To further investigate structure-activity relationship, a 3D model of ChPLA₂-IIA was built using the human intestinal phospholipase A₂ structure as template.

Conclusion

ChPLA2-IIA was purified to homogeneity using only two chromatographic colomns. Sequence analysis of the cloned cDNA indicates that the enzyme is highly basic with a pI of 9.0 and has a high degree of homology with mammalian intestinal PLA₂-IIA.

Importance of the residue Asp 290 on chain length selectivity and catalytic efficiency of recombinant Staphylococcus simulans lipase expressed in E. coli

In addition to their physiological importance, microbial lipases, like staphylococcal ones, are of considerable commercial interest for biotechnological applications such as detergents, food production, and pharmaceuticals and industrial synthesis of fine chemicals. The gene encoding the extracellular lipase of Staphylococcus simulans (SSL) was subcloned in the pET-14b expression vector and expressed in Esherichia coli BL21 (DE3). The wild-type SSL was expressed as amino terminal His6-tagged recombinant protein. One-step purification of the recombinant lipase was achieved with nickel metal affinity column. The purified His-tagged SSL (His6-SSL) is able to hydrolyse triacylglycerols without chain length selectivity. The major differences among lipases are reflected in their chemical specificity in the hydrolysis of peculiar ester bonds, and their respective capacity to hydrolyse substrates having different physico-chemical properties. It has been proposed, using homology alignment, that the region around the residue 290 of Staphylococcus hyicus lipase could be involved in the selection of the substrate. To evaluate the importance of this environment, the residue Asp290 of Staphylococcus simulans lipase was mutated to Ala using site-directed mutagenesis. The mutant expression plasmid was also overexpressed in Esherichia coli and purified with a nickel metal affinity column. The substitution of Asp290 by Ala was accompanied by a significant shift of the acyl-chain length specificity of the mutant towards short chain fatty acid esters. Kinetic studies of wild-type SSL and its mutant D290A were carried out, and show essentially that the catalytic efficiency (k cat /K M ) of the mutant was affected. Our results confirmed that Asp290 is important for the chain length selectivity and catalytic efficiency of Staphylococcus simulans lipase.