The selective release of phospholipase A2 by resident mouse peritoneal macrophages.

Resident mouse peritoneal macrophages have three phospholipase activities: a phospholipase A2 active at pH 4.5, a Ca2+-dependent phospholipase A2 active at pH 8.5 and a phosphatidylinositol-specific phospholipase C activity. When macrophages are exposed to zymosan in culture, the cellular activity of pH-4.5 phospholipase A2 is diminished in a manner dependent on zymosan concentration and time of exposure, whereas the cellular activities of pH-8.5 phospholipase A2 and phospholipase C remain unchanged. The depletion of pH-4.5 phospholipase A2 activity from the cell is paralleled by a quantitative recovery of this activity in the culture medium in a manner similar to the cellular depletion and extracellular recovery of two lysosomal enzymes. This release is specifically elicited by an inflammatory substance such as zymosan, since macrophages incubated with 6 micrometer latex spheres retain pH-4.5 phospholipase A2 activity and lysosomal enzyme activities intracellularly.     

Characterization of the major phosphoinositide-specific phospholipase C of human amnion

Most of the phosphoinositide-specific phospholipase C activity in human amnion at term was found to be attributable to a single isoform (Mr 85,000). Phospholipase C purified from amnion catalyzed the calcium-dependent hydrolysis of both phosphatidylinositol and phosphatidylinositol 4,5-bisphosphate. The high phospholipase C activity of amnion cells isolated at 38-41 weeks of gestation declined greater than 80% during the initial 2-5 days of culture to values characteristic of amnion tissue in early gestation. Activities of phospholipase A2 and phosphatidylinositol synthase remained essentially unaltered during this period of culture. Loss of phospholipase C activity was apparently due neither to the appearance of an inhibitor nor to the loss of an activator and most likely reflected a decrease in the amount of enzyme in amnion cells. Basal production of prostaglandin E2 (PGE2) by amnion cells also declined greatly during the period of loss of phospholipase C activity. Involvement of phospholipase C in the regulation of amnion prostaglandin production was also supported by the finding that the phospholipase C inhibitor, U-73122, potently inhibited amnion cell PGE2 production. In contrast, vasopressin, which appears to stimulate prostaglandin production in amnion cells by a phospholipase C-dependent mechanism, was equipotent in stimulating PGE2 production by amnion cells on Day 2 and Day 5 of culture, even though phospholipase C activity had declined by more than 75%. Furthermore, epidermal growth factor stimulation of PGE2 production by amnion cells appeared to be largely attributable to an increase in prostaglandin H synthase activity and did not involve an increase in phospholipase C activity.(ABSTRACT TRUNCATED AT 250 WORDS)     

Choline and betaine as inducer agents of Pseudomonas aeruginosa phospholipase C activity in high phosphate medium

In Pseudomonas aeruginosa, choline or betaine employed as the sole carbon and nitrogen source in a high phosphate medium induced a phospholipase C and an acid phosphatase activity but not an alkaline phosphatase activity. The P. aeruginosa strain utilized in this work does not possess a constitutive phospholipase C, since under culture conditions identical to those utilized by other authors (J. Bacteriol. 93, 670-674 (1967) and J. Bacteriol. 150, 730-738 (1982), our phospholipase C proved to be an inorganic phosphate-repressible enzyme. These findings enable us to conclude that although the phosphate control for the synthesis of phospholipase C may exist, it is expressed only under certain favorable culture conditions.     

Identification of a phosphatidylcholine active phospholipase C in human gallbladder bile

This study describes the identification of a phospholipase C activity against phosphatidylcholine in delipidated human gallbladder bile. All biles were obtained from cholesterol gallstone patients and were negative on bacterial culture. The biliary enzyme was inhibited by EDTA and had a pH optimum of between 7-8. All of the 15 gallbladders examined contained significant phospholipase C activity (32.85 +/- 8.37 nmol/h/mg delipidated protein). The finding of a phospholipase C in gallbladder bile of patients with cholesterol gallstones may be one of the factors responsible for or related to the rapid in vitro nucleation seen in these biles.     

Lethal Toxin of Bacillus cereus I. Relationships and Nature of Toxin, Hemolysin, and Phospholipase

Bacillus cereus phospholipase was characterized as a phospholipase C by the analysis of lecithin degradation products by thin-layer and paper chromatography. Methanol in the growth menstruum inhibited completely the synthesis of phospholipase C, whereas the synthesis of lethal toxin and hemolysin were only partially inhibited. Dialysis of preformed B. cereus products against ethyl alcohol and methanol did not inactivate hemolytic, phospholipase C, or lethal activity. The hemolytic and lethal activities of culture filtrates were completely abolished by trypsin, but phospholipase C activity was resistant to inactivation. Lethal and phospholipase C properties of culture filtrates were resistant to inactivation at 45 C, whereas the hemolytic activity was completely destroyed. Lethal, hemolytic, and phospholipase C activities appeared simultaneously in a complex growth menstruum, but the kinetics of synthesis were different in all cases. Resolution of B. cereus filtrates on columns of Sephadex showed that the phospholipase C, hemolysin, and lethal toxin are distinct proteins. Evidence is also presented which suggests a correlation between the synthesis of B. cereus toxin and the period of transition from vegetative growth to sporulation. The activity of each B. cereus product was cation-independent, as opposed to cation-dependency of the phospholipase C and lethal activities of Clostridium perfringens alpha-toxin. Immunological cross-reactivity between the B. cereus products and C. perfringens alpha-toxin was not apparent; indeed, they were shown to be antigenically distinct.     

A Novel Phospholipase C Inhibitor,S-PLI Produced by Streptomyces Sp. Strain No. A-6288

Abstract

S-PLI, an inhibitor of phospholipase C (PLC) produced by Strepromyces sp. strain No. 6288, was purified from the culture filtrate by salting-out with solid ammonium sulfate, column chromatography on CM-cellulose and gel filtration on Sephadex G-75. The molecular weight of S-PLI was estimated to be 65,000 by SDS-polyacrylamide gel electrophoresis. The inhibitor was found to be a glycoprotein with a composition of 609 amino acids and 19 glucose residues having an isoelectric point at 7.8. S-PLI was stable from pH 3 to 10 at 37°C and up to 40° at pH 6.0. The inhibitory activity showed pH-and temperature-dependence with a maximum around pH 7.0 at 50°C. S-PLI inhibited phospholipase C in a competitive manner (K_i value; 9.5 × 10-⁶ mM), but did not inhibit S-Hemolysin, phospholipase A₂, phospholipase B, phospholipase D and phosphatases. S-PLI is the first reported example of a glycoproteinaceous inhibitor of microbial origin which is able to specifically inhibit phospholipase C.     

Protein kinase C-mediated necrosis-apoptosis switch of cortical neurons by conditioned medium factors secreted under the serum-free stress

Cortical neurons die in necrosis in the low-density (LD) culture, and in apoptosis in the high-density (HD) culture under the serum-free condition without any supplements. The neuronal death in LD culture was delayed by conditioned medium (CM) factors prepared from the HD culture. The CM switched the cell death mode from necrosis to apoptosis, characterized by various cell death markers and transmission electron microscopy. The CM inhibited the rapid decrease in cellular ATP levels and [3H]-2-deoxy glucose ([3H]-2-DG) uptake in the LD culture. Inhibitors of phospholipase C and protein kinase C effectively abolished the CM-induced elevation of survival activity, [3H]-2-DG uptake and ATP levels, and necrosis-apoptosis switch. All these results suggest that CM caused the cell death mode switch from necrosis to apoptosis through phospholipase C- and protein kinase C-mediated mechanisms.     

Distribution and phospholipase activity of Candida species in different denture stomatitis types

The aim of this study was to evaluate the correlation between frequency and phospholipase activity of Candida species and denture stomatitis according to Newton’s classification. Seventy-five complete denture wearers were evaluated for the presence of yeasts on the palatal mucosa by culture method. In addition, the number of yeast isolates producing phospholipase and amount of this enzyme were determined using egg yolk agar plate method. According to Newton’s classification, 25 denture wearers were with healthy palatal mucosa while 50 were with any types of denture stomatitis. The frequency of yeasts was linked to whether subjects had Type II or Type III, but not Type I denture stomatitis. Candida albicans was the most frequently isolated species in denture wearers with and without clinical signs of denture stomatitis and it was the only species produced phospholipase. Although the amount of phospholipase produced by the C. albicans isolates from denture wearers in control and Type II and III DS groups was not significantly different, there was statistically significant difference in the number of C. albicans isolates producing phospholipase between patients with and without clinical signs of DS.     

Release of carrot plasma membrane-associated phosphatidylinositol kinase by phospholipase A2 and activation by a 70 kDa protein.

Plasma membranes were isolated from carrot (Daucus carota L.) cells grown in suspension culture and treated with phospholipase A2 from snake or bee venom for 10 min. As a result of this treatment, phosphatidylinositol kinase activity was recovered in the soluble fraction. There was no detectable diacylglycerol kinase or phosphatidylinositol monophosphate kinase activity released from the membranes after the phospholipase A2 treatment. Treating the plasma membranes with phospholipase C or D did not release PI kinase activity. The phospholipase A2-released PI kinase was activated over 2-fold by a heat stable, soluble 70 kDa protein. The partially purified 70 kDa activator increases the Vmax but does not affect the Km of the phospholipase A2-released PI kinase.     

Selective and programmed cleavage of GPI-anchored proteins from the surface membrane by phospholipase C

Many surface proteins of eukaryotic cells are tethered to the membrane by a GPI-anchor which is enzymatically cleavable. Here, we investigate cleavage and release of different GPI-proteins by phospholipase C from the outer membrane of the ciliate Paramecium tetraurelia. Our data indicate that different GPI-proteins are not equally cleaved as proteins of the surface antigen family are preferentially released in vitro compared to several smaller GPI-proteins. Likewise, the analysis of culture medium indicates exclusive in vivo release of surface antigens by two phospholipase C isoforms (PLC2 and PLC6). This suggests that phospholipase C shows affinity for select groups of GPI-anchored proteins. Our data also reveal an up-regulation of PLC isoforms in GPI-anchored protein cleavage during antigenic switching. As a consequence, silencing of these PLCs leads to a drastic decrease of antigen concentration in the medium. These results suggest a higher order of GPI-regulation by phospholipase C as cleavage occurs programmed and specific for single GPI-proteins instead of an unspecific shedding of the entire surface membrane GPI-content.     

Phosphatidyl inositol-specific phospholipase C from Clostridium novyi type A

From the culture broth of Clostridium novyi type A, phosphatidyl inositol-specific phospholipase C was separated from the major part of phospholipase C (γ-toxin) which hydrolyzes phosphatidyl choline, phosphatidyl ethanolamine, and sphingomyelin. Sodium deoxycholate stimulated the activity of phosphatidyl inositol phospholipase C. The concentration of sodium deoxycholate for maximal stimulation was 0.2% with 2 mm phosphatidyl inositol. Divalent cations (Mg²⁺, Ca²⁺, and Zn²⁺) were rather inhibitory above 10^?3m. Phosphatidyl inositol phospholipase C was not inhibited by EDTA or o-phenanthroline. When phosphatidyl inositol phospholipase C was incubated with rat liver slices, not only alkaline phosphatase but also 5′-nucleotidase was liberated into the soluble fraction.     

A comparison of phospholipase activity, cellular adherence and pathogenicity of yeasts

Phospholipase A and lysophospholipase activities were measured in the culture fluid and in the blastospores of Candida albicans. When phospholipase activity was measured in six yeasts (four strains of C. albicans and a single strain each of Candida parapsilosis and Saccharomyces cerevisiae) a correlation was found between this activity and two potential parameters of pathogenicity. The C. albicans isolates which adhered most strongly to buccal epithelial cells and were most pathogenic in mice had the highest phospholipase activities. Non-pathogenic yeasts, including C. albicans isolates which did not adhere and did not kill mice, had lower phospholipase activities.     

Determination of phosphatidylcholine in a flow injection system using immobilized enzyme reactors

Two alternative procedures are described for the quantitative determination of phosphatidylcholine in a flow-injection system utilizing immobilized enzymes. Phospholipase C from Bacillus cereus and phospholipase D from cabbage were covalently bound to the surface of controlled-pore glass beads and the enzyme-derivatized beads were packed in small columns. In the first procedure, the phospholipase C column was connected with a second column containing coimmobilized alkaline phosphatase and choline oxidase. In the alternative procedure, the column packed with immobilized phospholipase D was connected with a column packed with immobilized choline oxidase. The hydrogen peroxide produced through the action of choline oxidase in both flow-injection systems was detected amperometrically. Both procedures are suitable for an accurate and rapid quantitation of phosphatidylcholine. The sensitivity of the method based on phospholipase C and alkaline phosphatase is higher than that using phospholipase D. Quantitation of phosphatidylcholine at the nanomole level can be easily obtained using the first method.     

Comparison of phospholipase production in shape Cryptococcus neoformans isolates from AIDS patients and bird droppings

Secreted phospholipase has been recently proposed as a virulence determinant in Cryptococcus neoformans as well as Candida albicans. This issue of cryptococcal phospholipase requires screening of phospholipase production in a larger number of isolates from clinical and environmental sources. In this study we examined phospholipase production in a total of 67 C. neoformans isolates from AIDS patients and bird droppings by using the egg-yolk plate method. Phenoloxidase activity, capsule size and growth at 37 °C were also measured in these strains in order to observe a possible relationship between phospholipase production of different C. neoformans strains and its virulence. Four of the 21 AIDS strains at 28 °C and 1 at 37 °C did not produce phospholipase, respectively. In contrast, 38 and 34 of the 46 bird dropping strains were negative for phospholipase production at 28, and 37 °C, respectively. Statistical analysis revealed a significant difference in phospholipase production, capsule size and growth ability at 37 °C, but not phenoloxidase activity, between the AIDS and the bird dropping strains. The highly prevalent distribution of phospholipase activity in the AIDS strains suggests a role of the enzyme in invading the host. This revised version was published online in June 2006 with corrections to the Cover Date.     

Ca2+ regulation of phosphatidylinositol turnover in the plasma membrane of tobacco suspension culture cells.

The biochemical properties of the enzymes involved in phosphatidylinositol (PI) turnover in higher plants were investigated using the plasma membrane isolated from tobacco suspension culture cells by aqueous two-phase partitioning. Submicromolar concentrations of Ca2+ inhibited PI kinase and phosphatidylinositol 4-phosphate (PIP) kinase and stimulated phospholipase C. Diacylglycerol (DG) kinase was inhibited by Ca2+, but required a higher concentration than the physiological level. From the above results we postulate the following scheme: signal coupled activation of phospholipase C produces IP3 which induces Ca2+ release from the intracellular Ca2+ compartment, the increased cytoplasmic Ca2+ in turn activates phospholipase C and causes a further increase of the cytoplasmic Ca2+ level. This inhibits PI kinase and PIP kinase and brings about a limited supply of PIP2, the substrate of phospholipase C. Consequently, IP3 production decreases and Ca2+ mobilization ceases. Then cytosolic Ca2+ returns to the stationary level by the Ca2+ pump at the plasma membrane and at the endoplasmic reticulum and Ca2+/H+ antiporter at the plasma membrane and at the tonoplast.     

四株高产磷脂酶C新菌株的鉴定和分类

在前面研究高产磷脂酶C(PLC)菌株筛选及其抗血小板功能的基础上,对新筛选的四株高产PLC的754-1、779、970和1107菌株进行了鉴定和分类。通过形态特征、培养特征、生理生化特征以及16S rRNA序列测定及其同源性分析,证实754-1菌株与Bacillus cereus基本一致,因此将754-1菌株分类属于蜡状芽孢杆菌,命名为蜡状芽孢杆菌深圳株754-1,B．cereus shenzhen 754-1 strain。而779、970和1107三株菌则与Bacillus mycoides基本一致,因而将这三株菌分类属于蕈状芽孢杆菌,分别命名为蕈状芽孢杆菌深圳株779,B．mycoides shenzhen 779 strain,草状芽孢杆菌深圳株970,B．mycoides shenzhen 970 strain,和蕈状芽孢杆菌深圳株1107,B．mycoides shenzhen 1107 strain。这将为进一步利用这些菌株及其PLC打下坚实的基础。     

Strain-dependent effects of environmental signals on the production of extracellular phospholipase by Cryptococcus neoformans

Extracellular phospholipase (PL) activities comprising phospholipase B, lysophospholipase and lysophospholipase transacylase have been identified in culture supernatants of Cryptococcus neoformans and contribute to virulence. We found that PL production was optimal after fungal growth at 30 degrees C and secretion at 37 degrees C for all six C. neoformans isolates studied (four C. neoformans var. neoformans and two C. neoformans var. gattii). No increase in PL activity was found in one strain, NU-2, in low iron or tissue culture media, conditions where upregulation of other virulence factors has been reported. The most virulent strains in an intravenous mouse model of infection were best able to produce PL at growth and secretion temperatures of 37 degrees C, in tissue culture media and under assay conditions of pH 7.0.     

Improved Assay Method for Phospholipase C

A lecithin sol dispersed with deoxycholate was found to be attacked by phospholipase C in the presence of calcium ion more rapidly than were any other lecithin sols. The inorganic phosphate could be released quantitatively from the acid soluble phosphate liberated from lecithin by an excess amount of alkaline phosphatase present in phospholipase C reaction mixture. A simple and accurate assay method for phospholipase C was developed with the sol and the alkaline phosphatase.     

Phospholipase C (heat-labile hemolysin) of Pseudomonas aeruginosa: purification and preliminary characterization.

Phospholipase C (heat-labile hemolysin) was purified from Pseudomonas aeruginosa culture supernatants to near homogeneity by ammonium sulfate precipitation followed by a novel application of DEAE-Sephacel chromatography. Enzymatic activity remained associated with DEAE-Sephacel even in the presence of 1 M NaCl, but was eluted with a linear gradient of 0 to 5% tetradecyltrimethylammonium bromide. Elution from DEAE-Sephacel was also obtained with 2% lysophosphatidylcholine, and to a lesser extent with 2% phosphorylcholine, but not at all with choline. The enzyme was highly active toward phospholipids possessing substituted ammonium groups (e.g., phosphatidycholine, lysophosphatidylcholine, and sphingomyelin); however, it had little if any activity toward phospholipids lacking substituted ammonium groups (e.g., phosphatidylethanolamine, phosphatidylserine, and phosphaditylglycerol). Collectively, these data suggest that phospholipase C from P. aeruginosa exhibits high affinity for substituted ammonium groups, but requires an additional hydrophobic moiety for optimum binding. The specific activity of the purified enzyme preparation increased 1,900-fold compared with that of culture supernatants. The molecular weight of the phospholipase C was estimated to be 78,000 by both sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Sephacryl S-200 column chromatography and was 76,000 by high-performance size exclusion chromatography. The isoelectric point was 5.5. Amino acid analysis showed that phospholipase C was rich in glycine, serine, threonine, aspartyl, glutamyl, and aromatic amino acids, but was cystine free.     

The role of phospholipases from inflammatory macrophages in demyelination

Activated macrophages harvested from rat peritoneum were shown to contain phospholipase A₁, A₂ and lysophospholipase activities which were defined on a series of radiolabelled phospholipid substrates. During in vitro culture of these elicited macrophage populations, phospholipase enzymes were secreted into the culture medium. Radiolabelled myelin, prepared from young rats after intracerebral injection of¹⁴C acetate, was used as a substrate to analyze the susceptibility of central nervous system (CNS) myelin to attack by cell-associated and secreted macrophage enzymes. Homogenates of peritoneal macrophages degraded the myelin lipids at acid pH; phosphatidyl choline (PC) and ethanolamine phosphatide (EP) were both degraded with liberation of free fatty acid and small amounts of lysolipids. The ethanolamine lipids were most vulnerable; up to 20% of this fraction was degraded in six hours. Selected batches of macrophage culture supernatant similarly degraded the myelin EP at acid pH. These results suggest that phospholipase enzymes, released from activated macrophages in close proximity to the myelin sheath, may participate in primary demyelination in inflammatory CNS lesions.