Novel Stable Protease Inhibitor from Phoenix dactylifera(L.) Flowers with Antimicrobial and Antitumoral Activities

A novel protease inhibitor isolated from date palm Phoenix dactylifera(L.) flowers (PIDF) was purified and characterized. A heat and acidic treatment step followed by ethanol precipitation and reverse-phase high-performance chromatography was applied to purify this natural protease inhibitor to homogeneity with a single band of about 19 kDa. The stability study depicted that PIDF was fully stable at 40 °C and retained 65% of its initial activity after heating at 50 °C for 24 h. Its thermal stability at 70 °C was markedly enhanced by adding calcium, bovine serum albumin, and sorbitol as well as by metal divalent cations, especially Mg2+ and Hg2+. This protease inhibitor showed high inhibitory activity against therapeutic proteases, including pepsin, trypsin, chymotrypsin, and collagenase, and acted as a potent inhibitor of some commercial microbial proteases from Aspergillus oryzae, Bacillus. sp, and Bacillus licheniformis. Moreover, a potent antibacterial spectrum against Gram (+) and Gram (-) bacterial strains and an efficient antifungal effect were observed. Its cytotoxicity toward human colorectal cancer cell LoVo and HCT-116 lines suggested that PIDF could serve as a new therapeutic target inhibiting human colorectal cancer.

Functional Characterization and Anti-Tumor Effect of a Novel Group II Secreted Phospholipase A2 from Snake Venom of Saudi Cerastes cerates gasperetti

Secreted phospholipases A2 are snake-venom proteins with many biological activities, notably anti-tumor activity. Phospholipases from the same snake type but different geographical locations have shown similar biochemical and biological activities with minor differences in protein sequences. Thus, the discovery of a new phospholipase A2 with unique characteristics identified in a previously studied venom could suggest the origins of these differences. Here, a new Group II secreted phospholipase A2 (Cc-PLA2-II) from the snake venom of Saudi Cerastes cerastes gasperetti was isolated and characterized. The purified enzyme had a molecular weight of 13.945 kDa and showed high specific activity on emulsified phosphatidylcholine of 1560 U/mg at pH 9.5 and 50 °C with strict calcium dependence. Interestingly, stability in extreme pH and high temperatures was observed after enzyme incubation at several pH levels and temperatures. Moreover, a significant dose-dependent cytotoxic anti-tumor effect against six human cancer cell lines was observed with concentrations of Cc-PLA2 ranging from 2.5 to 8 µM. No cytotoxic effect on normal human umbilical-vein endothelial cells was noted. These results suggest that Cc-PLA2-II potentially has angiogenic activity of besides cytotoxicity as part of its anti-tumor mechanism. This study justifies the inclusion of this enzyme in many applications for anticancer drug development.

Structure and binding of the C-terminal segment of R9AP to lipid monolayers

Phototransduction cascade takes place in disc membranes of photoreceptor cells. Following its activation by light, rhodopsin activates the G-protein transducin causing the dissociation of its GTP-bound α-subunit, which in turn activates phosphodiesterase 6 (PDE6) leading to the hyperpolarization of photoreceptor cells. PDE6 must then be inactivated to return to the dark state. This is achieved by a protein complex which is presumably anchored to photoreceptor disc membranes by means of the transmembrane C-terminal segment of RGS9-1-Anchor Protein (R9AP). Information on the secondary structure and membrane binding properties of the C-terminal segment of R9AP is not yet available to further support its role in the membrane anchoring of this protein. In the present study, circular dichroism and infrared spectroscopy measurements have allowed us to determine that the C-terminal segment of human and bovine R9AP adopts an α-helical structure in solution. Moreover, this C-terminal segment has shown affinity for most of the phospholipids typical of photoreceptor membranes. In fact, the physical state and the type of phospholipid as well as electrostatic interactions influence the binding of the human and bovine peptides to phospholipid monolayers. In addition, these measurements revealed that the human peptide has a high affinity for saturated phosphocholine, which may suggest a possible localization of R9AP in photoreceptor microdomains. Accordingly, infrared spectroscopy measurements have allowed determining that the C-terminal segment of R9AP adopts an ordered α-helical structure in the presence of saturated phospholipid monolayers. Altogether, these data are consistent with the typical α-helical secondary structure and behavior observed for transmembrane segments and with the proposed role of membrane anchoring of the C-terminal segment of human and bovine R9AP.

Interaction of the Spo20 membrane-sensor motif with phosphatidic acid and other anionic lipids, and influence of the membrane environment

The yeast protein Spo20 contains a regulatory amphipathic motif that has been suggested to recognize phosphatidic acid, a lipid involved in signal transduction, lipid metabolism and membrane fusion. We have investigated the interaction of the Spo20 amphipathic motif with lipid membranes using a bioprobe strategy that consists in appending this motif to the end of a long coiled-coil, which can be coupled to a GFP reporter for visualization in cells. The resulting construct is amenable to in vitro and in vivo experiments and allows unbiased comparison between amphipathic helices of different chemistry. In vitro, the Spo20 bioprobe responded to small variations in the amount of phosphatidic acid. However, this response was not specific. The membrane binding of the probe depended on the presence of phosphatidylethanolamine and also integrated the contribution of other anionic lipids, including phosphatidylserine and phosphatidyl-inositol-(4,5)bisphosphate. Inverting the sequence of the Spo20 motif neither affected the ability of the probe to interact with anionic liposomes nor did it modify its cellular localization, making a stereo-specific mode of phosphatidic acid recognition unlikely. Nevertheless, the lipid binding properties and the cellular localization of the Spo20 alpha-helix differed markedly from that of another amphipathic motif, Amphipathic Lipid Packing Sensor (ALPS), suggesting that even in the absence of stereo specific interactions, amphipathic helices can act as subcellular membrane targeting determinants in a cellular context.

Enzymatic activity of Lecithin:retinol acyltransferase: a thermostable and highly active enzyme with a likely mode of interfacial activation

Lecithin:retinol acyltransferase (LRAT) plays a major role in the vertebrate visual cycle. Indeed, it is responsible for the esterification of all-trans retinol into all-trans retinyl esters, which can then be stored in microsomes or further metabolized to produce the chromophore of rhodopsin. In the present study, a detailed characterization of the enzymatic properties of truncated LRAT (tLRAT) has been achieved using in vitro assay conditions. A much larger tLRAT activity has been obtained compared to previous reports and to an enzyme with a similar activity. In addition, tLRAT is able to hydrolyze phospholipids bearing different chain lengths with a preference for micellar aggregated substrates. It therefore presents an interfacial activation property, which is typical of classical phospholipases. Furthermore, given that stability is a very important quality of an enzyme, the influence of different parameters on the activity and stability of tLRAT has thus been studied in detail. For example, storage buffer has a strong effect on tLRAT activity and high enzyme stability has been observed at room temperature. The thermostability of tLRAT has also been investigated using circular dichroism and infrared spectroscopy. A decrease in the activity of tLRAT was observed beyond 70°C, accompanied by a modification of its secondary structure, i.e. a decrease of its α-helical content and the appearance of unordered structures and aggregated β-sheets. Nevertheless, residual activity could still be observed after heating tLRAT up to 100°C. The results of this study highly improved our understanding of this enzyme.

Comparison between the behavior of different hydrophobic peptides allowing membrane anchoring of proteins

Membrane binding of proteins such as short chain dehydrogenase reductases or tail-anchored proteins relies on their N- and/or C-terminal hydrophobic transmembrane segment. In this review, we propose guidelines to characterize such hydrophobic peptide segments using spectroscopic and biophysical measurements. The secondary structure content of the C-terminal peptides of retinol dehydrogenase 8, RGS9-1 anchor protein, lecithin retinol acyl transferase, and of the N-terminal peptide of retinol dehydrogenase 11 has been deduced by prediction tools from their primary sequence as well as by using infrared or circular dichroism analyses. Depending on the solvent and the solubilization method, significant structural differences were observed, often involving α-helices. The helical structure of these peptides was found to be consistent with their presumed membrane binding. Langmuir monolayers have been used as membrane models to study lipid-peptide interactions. The values of maximum insertion pressure obtained for all peptides using a monolayer of 1,2-dioleoyl-sn-glycero-3-phospho-ethanolamine (DOPE) are larger than the estimated lateral pressure of membranes, thus suggesting that they bind membranes. Polarization modulation infrared reflection absorption spectroscopy has been used to determine the structure and orientation of these peptides in the absence and in the presence of a DOPE monolayer. This lipid induced an increase or a decrease in the organization of the peptide secondary structure. Further measurements are necessary using other lipids to better understand the membrane interactions of these peptides.

Enzymatic properties of stingray Dasyatis pastinaca group V, IIA and IB phospholipases A(2): a comparative study

In the present study, we have purified the group V phospholipase from the heart of cartilaginous fish stingray Dasyatis pastinaca and compared its biochemical properties with group IIA (sPLA2-IIA) and IB (sPLA2-IB) phospholipases previously purified from pancreas and intestine, respectively. Group V phospholipase (sPLA2-V) was purified to homogeneity by heat treatment, ammonium sulphate precipitation and RP-HPLC. The N-terminal sequence of the purified sPLA2-V exhibits a high degree of homology with those of mammal. The enzyme was found to be monomeric with a molecular mass estimation of 14 kDa. The specific activity of the purified enzyme, measured at pH 8 and 37 °C was 52 U/mg. Like sPLA2-IB and sPLA2-IIA, the sPLA2-V is found to be stable between pH 3 and 11 after 30 min of incubation. The purified sPLA2-V retained 65% of its activity after 10 min of incubation at 70 °C and it absolutely requires Ca(2+) for enzymatic activity. In addition it displayed high tolerance to organic solvents. Kinetic parameters Kmapp, kcat and the deduced catalytic efficiency (kcat/Kmapp) of the purified group-V, -IB and -IIA PLA2s were determined using phosphatidylethanolamine (PE), phosphatidylcholine (PC) or phosphatidylserine (PS) as substrate. The three enzymes hydrolyze the zwiterionic PE and PC substrates more efficiently than anionic PS substrate.

Antibacterial properties of intestinal phospholipase A2 from the common stingray Dasyatis pastinaca

Stingray phospholipase A(2) group IIA (SPLA(2)-IIA) was recently isolated and purified to homogeneity from the intestine of the common stingray Dasyatis pastinaca, suggesting that this enzyme plays an important role in systemic bactericidal defense. The present study showed that SPLA(2)-IIA was highly bactericidal against Gram-positive bacteria with inhibition zones and minimal inhibitory concentration values in the range of 13-25 mm and 2-8 μg/ml, respectively, whereas Gram-negative bacteria exhibited a much higher resistance. The bactericidal efficiency of SPLA(2)-IIA was shown to be unaffected by high protein and salt concentrations, but dependent upon the presence of calcium ions, and then correlated to the hydrolytic activity of membrane phospholipids. Importantly, we showed that stingray phospholipase A(2) group IIA presents no cytotoxicity after its incubation with MDA-MB-231 cells. SPLA(2)-IIA may be considered as a future therapeutic agent against bacterial infections.

Purification, biochemical and kinetic properties of recombinant Staphylococcus aureus lipase

We have compared the purification procedures as well as the biochemical and kinetic properties of wild type (wt-SAL3), untagged recombinant (rec(-His)SAL3), and tagged recombinant (rec(+His)SAL3) purified forms of Staphylococcus aureus lipase (SAL3). We used the pH-stat method (with emulsified tributyrin and olive oil as substrates) and the monomolecular film technique (with the three dicaprin isomers spread in the form of monomolecular films at the air-water interface). The data obtained showed that the recombinant expression process as well as the presence of a his-tag at the N-terminus of recombinant SAL3 affects significantly many biochemical and catalytic properties. The effects of the heterologous expression process on the catalytic properties of the staphylococcal lipases are three times more deleterious than the presence of an N-terminal tag extension.

Heterologous expression and N-terminal His-tagging processes affect the catalytic properties of staphylococcal lipases: a monolayer study

The interfacial and kinetic properties of wild type, untagged recombinant and tagged recombinant forms of three staphylococcal lipases (SSL, SXL and SAL3) were compared using the monomolecular film technique. A kinetic study on the dependence of the stereoselectivity of these nine lipase forms on the surface pressure was performed using the three dicaprin isomers spread in the form of monomolecular films at the air-water interface. New parameters, termed Recombinant expression Effects on Catalysis (REC), N-Tag Effects on Catalysis (TEC), and N-Tag and Recombinant expression Effects on Catalysis (TREC), were introduced. The findings obtained showed that with all the lipases tested, the recombinant expression process and the N-terminal His-tag slightly affect the sn-1 preference for dicaprin enantiomers as well as the penetration capacity into monomolecular films of phosphatidylcholine but significantly decrease the catalytic rate of hydrolysis of three dicaprin isomers. This rate reduction is more pronounced at high surface pressures, i.e. at low interfacial energies. In conclusion, the effects of the heterologous expression process on the catalytic properties of the staphylococcal lipases are three times more deleterious than the presence of an N-terminal tag extension. In the case of the situation most commonly encountered in the literature, i.e. the heterologous expression of a tagged lipase, the rate of catalysis can be decreased by these processes by 42-83% on average in comparison with the values measured with the corresponding wild type form.

Enzymatic synthesis of eugenol benzoate by immobilized Staphylococcus aureus lipase: optimization using response surface methodology and determination of antioxidant activity

The ability of a non-commercial immobilized Staphylococcus aureus lipase to catalyze the esterification of eugenol with benzoic acid was checked and the antioxidant power of the ester formed was evaluated. Response surface methodology based on four variables (the reaction temperature, the amount of lipase, the benzoic acid/eugenol molar ratio and the volume of solvent) was used to optimize the experimental conditions of eugenol benzoate synthesis. The maximum conversion yield (75%) was obtained using 240 IU of immobilized lipase, a benzoic acid/eugenol molar ratio of 1.22 dissolved in 4.6 ml chloroform at 41 degrees Celsius. The antioxidant activities of eugenol and its ester were evaluated. Compared to BHT, used as a model synthetic antioxidant, the eugenol benzoate showed a higher antioxidative activity. The IC(50) value for 1,1-diphenyl-2-picrylhydrazyl was found to be 18.2 microg/ml versus 20.2 microg/ml for eugenol and eugenol benzoate.

Staphylococcal lipases stereoselectively hydrolyse the sn-2 position of monomolecular films of diglyceride analogs. Application to sn-2 hydrolysis of triolein

Using the monomolecular film technique, a kinetic study on the stereoselectivity of nine staphylococcal lipase forms was carried out with three pairs of enantiomers from diglyceride analogs (didecanoyl-deoxyamino-O-methyl glycerol, DDG) containing a single hydrolysable decanoyl ester group and two lipase-resistant groups. Our results show that the kinetic profiles of the wild type, the recombinant untagged and the recombinant tagged forms of staphylococcal lipases are significantly different. As with most of the lipases investigated so far, these staphylococcal lipases showed higher catalytic rates with primary esters than with secondary esters. However, it is noteworthy that all these staphylococcal lipases were found to significantly hydrolyse the secondary ester group of diglyceride analogs, with a strong preference for the R configuration. This stereopreference, which was predicted on the basis of Kazlauskas' rule, was comparable to that of Candida rugosa and Pseudomonas glumae lipases. As was to be expected, all the staphylococcal lipases tested efficiently hydrolysed triolein at the sn-2 position. This hydrolytic activity was quantified by performing thin-layer chromatography to analyse the hydrolytic products of triolein. From the qualitative point of view, the sn-2 preferences observed with triolein and diglyceride analogs bearing a secondary ester function were in good agreement. Diglyceride analogs might therefore provide useful initial screening tools for use in future searches for strictly sn-2 specific lipases.

Crab digestive phospholipase: a new invertebrate member

Crab digestive phospholipase (CDPL) was purified from the hepatopancreas of Carcinus mediterraneus crabs. Homogeneous enzyme was obtained after two chromatography steps: anion exchange and size exclusion HPLC column. Homogeneous CDPL has a molecular mass of 14 kDa as determined by SDS/PAGE analysis. Unlike known digestive phospholipases like porcine PLA(2) (PPPL), CDPL displayed its maximal activity at 50 degrees C and not at 37 degrees C. A specific activity of 40 U/mg for the purified CDPL was measured using PC as substrate under optimal conditions (pH 8 and 50 degrees C) in the presence of 8 mM sodium deoxycholate (NaDC) and 10 mM CaCl(2). In contrast to PPPL, purified CDPL was completely inactivated at 60 degrees C. The N-terminal sequence was determined by automatic Edman degradation. No similarity between 12 N-terminal amino acid residues of CDPL was found with those of known digestive phospholipases. CDPL appears to be a new member of invertebrate phospholipases, and it is potentially useful for treat phospholipid-rich industrial effluents, or to synthesize useful chemical compounds which can be used in the food industry.

Involvement of Gly 311 residue on substrate discrimination, pH and temperature dependency of recombinant Staphylococcus xylosus lipase: A study with emulsified substrate

The importance of microbial lipases like the staphylococcal ones, results not only from their significance implication in the bacterial lipid metabolism but also their involvement in some pathogenic processes. The aminoacid sequence of the mature Staphylococcus xylosus lipase (SXL) shows 99.7% identity with the mature aminoacid sequence of Staphylococcus simulans lipase (SSL) with one substitution of Gly311 by Val. In spite of this high homology, the two lipases present significant differences in the specific activities and in the optimal temperature of action. In order to check the importance of the residue 311, we substituted, using site-directed mutagenesis, the Gly311 of S. xylosus lipase (SXL) by Leu, Trp, Asp, or Lys. The mutants SXL-G311L, SXL-G311W, SXL-G311D, and SXL-G311K were expressed in Escherichia coli BL21 (DE3) and purified to homogeneity. A comparative study of the biochemical properties of the wild-type SXL (SXL-WT) and the mutants was performed and show that an increase in the size of the 311 aminoacid side chain residue was accompanied by a decrease of lipase activity. The absence of lipase activity observed with the mutant SXL-G311W was probably due to the inaccessibility of substrate to interact with the catalytic serine. On the other hand, the SXL-G311L mutant, which presents a significant decrease on the lipase activity, displays a novel action towards phospholipids. Furthermore, the mutant SXL-G311L becomes also stable to extreme pH and displays a half life of 280 min after incubation at 50 degrees C. The purified SXL-G311D and SXL-G311K mutants show distinct pH profiles. The SXL-G311D mutant is optimally active at pH 6.5, whereas, the SXL-G311K mutant is active at pH 9.5. In addition, these two mutants show an important decrease in the specific activities that generates a decrease in the catalytic efficiency (k(cat)/K(m)app.). We can essentially notice that the SXL-G311K mutant displays a 33- or 44-fold decrease in k(cat)/K(m)app. values compared to the SXL-WT, when using TC(4) or TC(8) as substrate, respectively.

[Endobronchial pulmonary rhabdomyosarcoma. A case report]

We report a case of pleiomorphous pulmonary rhabdomyosarcoma observed in a 64-year-old patient with no history of soft tissue tumor. The tumor was found extending into the right lower and middle lobes. The intra-parenchymatous extension protruded into the middle lobular bronchus and was prolonged by a 4 cm polyp. The polyp extended up to the carina and reached the contralateral common bronchus. Outcome was fatal after surgery performed in an emergency setting due to asphyxia. Explorations could not be continued to determine the primary or secondary nature of the tumor. An intraparenchymatous endobronchial localization is uncommon. Primary rhabdomyosarcoma is generally a purely intra-parenchymatous tumor. The endobronchial localization has been described before but is very exceptional. This localization would also be exceptional for secondary rhabdomyosarcoma mimicking a primary malignant tumor. The histology study revealed an undifferentiated pleiomorphous tumor. Immunohistochemistry provided the final diagnosis.

[Thymolipoma. A case report]

Thymolipoma is an uncommon benign tumor of the thymus. Asymptomatic, it is an incidental discovery. Pathogenesis remains controversial. We report a new case in a 36-year-old woman that was discovered on a chest x-ray ordered for pneumonia. The MRI findings suggested the diagnosis which was confirmed at the pathology examination of the surgical specimen.

Hydatid disease of the liver with thoracic involvement

Hydatidosis, caused by Echinococcus granulosus, is an endemic parasitic disease in Mediterranean countries. The most frequent anatomic locations are liver and lung. Intrathoracic rupture of hydatid cysts situated in the hepatic dome is a serious complication resulting in damage to the pleura, pulmonary parenchyma, and bronchi. From January 1984 to December 1997 we operated on 40 patients with intrathoracic rupture of a hepatic hydatid cyst. Chest roentgenograms showed a shadow of varying size at the base of the hemithorax. Hepatic and thoracic ultrasonography was performed in all cases. The diagnosis of intrathoracic rupture of a liver cyst was confirmed preoperatively in 30 of the 40 cases. Posterolateral thoracotomy was performed in all patients. This transthoracic approach allowed adhesiolysis and treatment of the pleural lesions, pulmonary lesions, and hepatic cyst. Treatment of the diaphragmatic gap is easily done. We performed 15 lobectomies, 10 wedge resections, 16 decortications, and in one patient simple drainage of a voluminous pleuropulmonary and hepatic purulent hydatic collection. The postoperative course was uneventful in 26 cases, but 14 patients had complications, from which 3 patients died. The therapeutic approach depends on ultrasonographic findings. We believe ultrasonography to be the best examination for assessing biliary, hepatic, diaphragmatic, and pleuropulmonary lesions. When an intrathoracic collection is present, thoracotomy must be performed and is sufficient if the biliary tract is safe. An abdominal approach is necessary when biliary duct drainage is required, and it may be sufficient in cases of direct rupture into the bronchi.

[Bronchoesophageal fistula with late revelation]

Bronchoesophageal fistula is an uncommon clinical problem which can either occur as a congenital or acquired condition. A 40-year-old male had productive cough with production of sputum mixed with food particles and cough when eating and drinking. There was no weight loss nor weakness. Clinical examination led to the diagnosis of a fistula between the lower esophagus and the Nelson bronchus associated with bronchiectasis. The congenital nature of this fistula was suggested by the clinical, operative and pathology findings. Postoperative recover was uneventful. Esophageal respiratory tract fistula presenting in adult life are rare and can cause severe debilitation and suppurating lung disease. Surgical treatment provides complete resolution of the symptoms. Endoscopic obliteration can be considered as an alternative to surgery.

[Radiological and clinical aspects of bronchogenic lung cysts: 4 case reports]

Bronchogenic lung cysts are exceptional. We report four cases which raised a problem of differential diagnosis. Our patients included four women and a young boy (age range 12 - 36 years). The first patient consulted for bloody purulent sputum in a context of an infectious syndrome. The second patient had lower right-sided chest pain. The cyst was a fortuitous discovery in the other two cases. In one case, the chest x-ray disclosed a thin-walled cavity of the upper right lobe, confirmed on the CT scan which also evidenced intracavitary partitions. In two other cases, the chest x-ray showed a liquid-filled opacity (one in the lower right lobe and the other in the upper right lobe) and no further specificity on the CT scan. In the last case, a liquid-air cavity was evidenced. Upper right lobectomy was performed for the case with an air-filled cavity and tumorectomy for the other cases. Pathology reported bronchogenic cyst in all cases. The radiological and clinical presentations observed in patients with bronchogenic lung cysts, with or without tracheobronchial communication, are polymorphous, often raising problems of differential diagnosis.

[Costal chondrosarcoma. 4 cases]

BACKGROUND

Tumors of the rib cage are uncommon and malignant in 29% of the cases. Chondrosarcoma predominates, accounting for 40% of all cases of malignant costal tumors.

CASE REPORTS

Four patients (3 women, 1 man, mean age 28.2 years) were hospitalized for costal chondrosarcoma. Pain and tumefaction dominated the clinical presentation. Calcifications suggested the diagnosis in 3 cases. Curative surgery was performed in all cases. Postoperative radiotherapy was unable to improve prognosis in 2 patients.

DISCUSSION

Chondrosarcoma of the ribs is characterized by a strong potential for invasive extension. Diagnosis is suspected on the basis of imaging findings and confirmed at pathology. Surgery is required. Chemotherapy and radiotherapy do not improve prognosis significantly.

[Endo-bronchial lipoma. Apropos of a case]

We report a case of an endobronchial lipoma on a 63 year-old woman, treated surgically. A literature review allows us to show the importance of fiberoptic bronchoscopy and computerized tomography in the diagnosis of this kind of benign tumors. The different aspects of treatment with recent progress represented by endoscopic resection are studied.