Egg Yolk Factor of Staphylococcus aureus II. Characterization of the Lipase Activity

Bacterial Lipase Neutralized Toxicity of Lipopolysaccharide on Chicken Embryo Cardiac Tissue

It has been shown that near all organs, especially the cardiovascular system, are affected by bacterial lipopolysaccharide via the activation of Toll-like receptor signaling pathways. Here, we tried to find the blunting effect of bacterial lipase on lipopolysaccharide (LPS)-induced cardiac tissue toxicity in chicken embryos. 7-day fertilized chicken eggs were divided randomly into different groups as follows; Control, Normal Saline, LPS (0.1, 0.5 and 1 mg/kbw), and LPS (0.1, 0.5 and 1 mg/kbw) plus 5 mg/ml Lipase. On day 17, the hearts were sampled. The expression of genes such as GATA4, NKX2.5, EGFR, TRIF, and NF-ƙB was monitored using real-time PCR analysis. Using western blotting, we measured NF-ƙB protein level. Total antioxidant capacity, glutathione peroxidase, and Catalase activity were also studied. Microvascular density and anterior wall thickness were monitored in histological samples using H&E staining. High dose of LPS (1 mg/kbw) increased the expression of TRIF but not NF-ƙB compared to the control group (p < 0.05). We found a statistically significant reduction in groups that received LPS + Lipase compared to the control and LPS groups (p < 0.05). Western blotting revealed that the injection of Lipase could reduce LPS-induced NF-ƙB compared to the control group (p < 0.05). The expression of GATA4, NKx2.5, and EGFR was not altered in the LPS group, while the simultaneous application of LPS and Lipase significantly reduced GATA4, NKx2.5, and EGFR levels below the control (p < 0.05). We found non-significant differences in glutathione peroxidase, and Catalase activity in all groups (p > 0.05), while total antioxidant capacity was increased in groups that received LPS + Lipase. Anterior wall thickness was diminished in LPS groups and the use of both lipase and LPS returned near-to-control values (p < 0.05). Despite a slight increase in microvascular density, we found statistically non-significant differences in all groups (p > 0.05). Bacterial lipase reduces detrimental effects of LPS on chicken embryo heart induced via Toll-like receptor signaling pathway.

Evaluation of a fluorimetric assay on the lipases from strains of milk psychrotrophic bacteria

A fluorimetric assay, developed for the assay in milk of the lipase of the raw milk psychrotrophPseudomonas fluorescensAR11 (Stead, 1983), was evaluated in both buffer and in milk using cell-free lipase preparations from 11 strains of lipolytic psychrotrophic bacteria isolated from milk. Lipases of all strains were more active against 4-methylumbelliferyl nonanoate (4-MUN) than against 4-methylumbelliferyl oleate (4-MUO) in the buffer system but most were less active against 4-MUN than against 4-MUO in the milk assay system. In both systems, 4-MUO had a much lower rate of non-enzymic hydrolysis than did 4-MUN. Lipase activities measured by radial diffusion in tributyrin agar and trioctanoin agar reflected activities against 4-MUO and 4-MUN, except that lipase from a strain of coliform was relatively more reactive against the 4-MU esters. When compared with assay in the buffer system the most effectively activated lipase in the milk system was that from AR11; of those from other strains, 6 were 50–69% as effectively activated, 2 were about 17% and 2 were 7–8% activated. This difference in behaviour was related to the direct inhibition of lipases of some of the strains by the mixture of sodium taurocholate (NaTC) and cetyltrimethylammonium bromide (CTAB) needed in the milk assay system to dissociate lipase from milk protein. Increasing the proportion of NaTC to CTAB increased the activities of the more weakly activated lipases but decreased those of others. The assay in milk may therefore underestimate the lipase from certain strains of psychrotrophic bacteria.

Extracellular lipase of Aspergillus niger NRRL3; production, partial purification and properties

Four strains of Aspergillus niger were screened for lipase production. Each was cultivated on four different media differing in their contents of mineral components and sources of carbon and nitrogen. Aspergillus niger NRRL3 produced maximal activity (325U/ml) when grown in 3% peptone, 0.05% MgSO(4).7H(2)O, 0.05% KCl, 0.2% K(2)HPO(4) and 1% olive oil:glucose (0.5:0.5). A. niger NRRL3 lipase was partially purified by ammonium sulphate precipitation. The majority of lipase activity (48%) was located in fraction IV precipitated at 50-60% of saturation with a 18-fold enzyme purification. The optimal pH of the partial purified lipase preparation for the hydrolysis of emulsified olive oil was 7.2 and the optimum temperature was 60°C. At 70°C, the enzyme retained more than 90% of its activity. Enzyme activity was inhibited by Hg(2+) and K(+), whereas Ca(2+) and Mn(2+) greatly stimulated its activity. Additionally, the formed lipase was stored for one month without any loss in the activity.

Staphylococcal lipases: biochemical and molecular characterization

To date, the nucleotide sequences of nine different lipase genes from six Staphylococcus species, three from S. epidermidis, two from S. aureus, and one each from S. haemolyticus, S. hyicus, S. warneri, and S. xylosus, have been determined. All deduced lipase proteins are similarly organized as pre-pro-proteins, with pre-regions corresponding to a signal peptide of 35 to 38 amino acids, a pro-peptide of 207 to 321 amino acids with an overall hydrophilic character, and a mature peptide comprising 383 to 396 amino acids. The lipases are secreted in the pro-form and are afterwards processed to the mature form by specific proteases. The pro-peptide of the S. hyicus lipase is necessary for efficient translocation and for protection against proteolytic degradation. Despite being very similar in their primary structures the staphylococcal lipases show significant differences in their biochemical and catalytic properties, such as substrate selectivity, pH optimum and interfacial activation. The lipase from S. hyicus is unique among the staphylococcal and bacterial lipases in that it has not only lipase activity, but also a high phospho-lipase activity. All staphylococcal lipases are dependent on Ca(2+), which is thought to have a function in stabilizing the tertiary structure of the lipases. Evidence exists that staphylococcal lipases like other bacterial lipases, possess a lid-like domain that might be involved in the interfacial activation of these enzymes.

Staphylococcal lipases: molecular characterisation, secretion, and processing

Up to date five different staphylococcal lipase genes, two of Staphylococcus aureus (sal-1 and sal-2), two of Staphylococcus epidermidis (sel-1 and sel-2) and one of Staphylococcus hyicus (sh1) have been cloned and sequenced. All corresponding proteins are organised as pre-pro-enzymes: the pre-region represents the signal peptide, the pro-region has a length between 207 and 267 amino acids, and the mature part comprises 380 to 400 amino acids. We found that the lipases are secreted in the pro-lipase form. The processing of the pro-form to the mature enzyme occurs extracellular by a specific protease. Interestingly the pro-lipase reveals not much less activity compared to the mature lipase. There are evidences that the pro-region acts as an intramolecular chaperone which facilitates translocation not only of the native lipase but also of a number of completely unrelated proteins fused to the pro-peptide. It was also observed that the pro-region protects the proteins from proteolytic degradation. While the Staphylococcus aureus and Staphylococcus epidermidis lipases have only lipase (esterase) activity, the related Staphylococcus hyicus enzyme (SHL) is distinguished by both lipase and phospho-lipase activity. The biochemical and catalytic properties of these lipases are described in the accompanying article (Simons, J.W., Götz, F., Egmont, M.R. and Verheij, H.M., 1998. Staphylococcal lipases: Biochemical properties. Accompanying article).

Production, purification and characterization of Bacillus lipase

The lipolytic activities in the supernatant fractions of Bacillus cereus and Bacillus coagulans cultures were investigated. Aeration, agitation, different media, emulsified oils, inoculum size and phase of growth affected lipase production. Aeration was essential for lipase production (air: medium ration 4:1) and produced the highest activity. The lipolytic activity reached a maximum level after incubation for two days with continuous agitation. It was also elevated by the presence of either olive oil or tributyrin and with lesser extent in the presence of castor oil. The enzyme levels were drastically reduced in the presence of animal fat, cotton seed oil, margarine or glycerol. The extracellular lipase enzyme from Bacillus cereus was purified with 46.2% overall recovery thought too steps, an acetone precipitation of the whole supernatant and purification by gel filtration on sephadex G-100. The efficiency of the purification process was evaluated through the polyacrylamide gel electrophoresis. The enzyme has an optimum pH 7.5 at the optimum incubation temperature of 40 degrees C. It is stable and retains its full activity after heating at 40-50 degrees C for 30 min. The activity is lost completely at 80 degrees C.

Application of lipovitellin-salt-mannitol agar for screening, isolation, and presumptive identification of Staphylococcus aureus in a teaching hospital

Lipovitellin-salt-mannitol (LSM) plate medium was examined for its ability to directly isolate, recover, and presumptively identify Staphylococcus aureus from 418 clinical specimens. The criteria for medium evaluation included colony morphology reactions, selectivity, and ease of isolation. For 298 specimens used for screening, LSM agar medium was compared with the other conventional media used, mannitol salt agar (MSA), 5% horse blood agar (HBA), and phenolphthalein phosphate agar (PPA), to detect and recover S. aureus and methicillin-resistant S. aureus. The results indicated that LSM agar is more effective than MSA, HBA, or PPA for the recovery and isolation of S. aureus and methicillin-resistant S. aureus. On a replicator multipoint inoculation system, we compared the reactions on LSM agar, MSA, and DNase agar of 227 different strains of staphylococci, which included 178 different strains of S. aureus and 49 different strains of coagulase-negative staphylococci isolated from clinical specimens. By using the lipovitellin precipitation activity and mannitol fermentation characteristics, LSM agar gave a 100% correlation in presumptively identifying S. aureus. LSM agar may be an alternative plate medium for large hospital extensive screening for the detection and isolation of S. aureus.

Purification and characterization of extracellular Staphylococcus warneri lipase

The extracellular lipase of Staphylococcus warneri was secreted as a protein with an apparent molecular mass of 90 kDa. It was then sequentially processed in the supernatant to a protein of 45 kDa. Tryptic digestion of the crude extract resulted in a homogeneous sample containing only the 45-kDa form. Purification was achieved by hydrophobic chromatography. Purified lipase had an optimum pH of 9.0 and an optimum temperature of 25 degrees C. The enzyme was stable within the range pH 5.0-9.0; it had a broad substrate specificity. The results of inhibition studies were consistent with the view that lipases possess a serine residue at the catalytic site.

Cloning, nucleotide sequence and expression in Escherichia coli of a lipase gene from Bacillus subtilis 168

The gene coding for an extracellular lipase of Bacillus subtilis 168 was cloned and found to be expressed in Escherichia coli. Enzyme activity measurements showed no fatty acid chain length preference. A set of Tn5 insertions which inactivate the gene were localized and used to initiate its sequencing. The nucleotide sequence was determined on two independent clones expressed in E. coli. In one of these clones, the sequence revealed a frameshift, due to the presence of an additional adenine in the N-terminal region, which caused the interruption of the open reading frame, probably allowing translation to initiate at a second ATG codon. The sequence of the wild-type lip gene from B. subtilis was confirmed on the chromosomal fragment amplified by polymerase chain reaction (PCR). When compared to other lipases sequenced to date, the enzyme described here lacks the conserved pentapeptide Gly-X-Ser-X-Gly supposed to be essential for catalysis. However, alignments of several microbial lipase sequences suggest that the pentapeptide Ala-X-Ser-X-Gly present in the lipase B. subtilis may function as the catalytic site. Homologies were found in the N-terminal protein region with lipases from different Pseudomonas species. The predicted M(r) and isoelectric point for the mature protein are 19,348 and 9.7 respectively.

Substrate specificity of Staphylococcus aureus (TEN5) lipases with isomeric oleoyl-sn-glycerol ethers as substrates

For the first time fully protected substrates with only one hydrolyzable ester bond have been used to analyze the substrate specificity of microbial lipases. In these substrates the ester is attached to the glycerol molecule in a precisely defined position. The use of three different substituents generates chirality and thus allows the analysis of positional specificities of individual lipases. Therefore, these new substrates have been used to study the enzymatic activities of two closely related lipases isolated from Staphylococcus aureus (TEN5) designated the 44 and 43 kDa lipase. The lipases, especially the 44 kDa molecule, show a high specificity for the hydrolysis of the ester in the sn-1 position (S-configuration), which is hydrolyzed by a factor of ten faster than that in the sn-3 position. In addition, the study demonstrates for the first time that the rate of hydrolysis of a fatty acid ester attached to the sn-2 position of glycerol by microbial lipases depends on the configuration of the substrate molecule.

Complete nucleotide sequence of the lipase gene from Staphylococcus hyicus cloned in Staphylococcus carnosus

The lipase gene from Staphylococcus hyicus subsp. hyicus was cloned in Staphylococcus carnosus and Escherichia coli. In both host organisms the lipase gene is expressed and the enzyme is released to the medium. The cloned DNA insert is 2.5 kb in length and DNA sequencing has revealed the location of the gene, the ribosomal binding site and the presence of a typical signal sequence. The open reading frame comprises 1923 nucleotides and gives a preprotein of 641 amino acids with a predicted Mr of 71.382. At the 3' end of the structural gene there are three consecutive stop codons and there is also a transcriptional termination signal.

Purification and some properties of the staphylococcal extracellular lipase

Staphylococcal lipase has been purified by application of a multistep procedure involving ammonium sulfate precipitation, and hydrophobic interaction chromatography followed by gel filtration through Sepharose CL-4B. A purified enzyme was obtained which appeared to be homogeneous by molecular sieving, polyacrylamide gel electrophoresis and sucrose gradient centrifugation. The enzyme was then subjected to physicochemical analysis. It has been found that staphylococcal lipase appears in two molecular forms: light (45 kDa) and heavy (300 kDa). Amino acid analysis indicates that lipase contains 17 amino acids with a prevalence of hydrophobic amino acids. No sulfur-containing amino acid was found in the enzyme molecule. The lipase contains about 2% sugars and some amount of lipids. The lipase preparation is stable within pH 5.0 to 9.0 and exhibits maximal activity at pH 8.0. The optimal temperature for the enzymatic reaction was established at 55 degrees C.

Separation and characterization of two isolated lipases from Staphylococcus aureus (TEN5)

The purified lipases from Staphylococcus aureus (TEN5) showing two enzymatically active protein bands on SDS-polyacrylamide gel electrophoresis have been separated by ion-exchange chromatography. The separated proteins show some properties which are different (e.g., apparent molecular weight, charge, binding of detergent, enzymatic activity towards triolein) and some which are almost identical (spur in immunodiffusion).

The identification of staphylococci in clinical and food microbiology laboratories

A comprehensive review of the methods which have been utilized for the identification of staphylococci is presented. Biochemical characteristics which have assisted in the primary isolation of staphylococci, such as pigmentation, hemolytic activity, the egg yolk phenomenon, and deoxyribonuclease and coagulase production, are also analyzed. The potential applicability of advanced techniques to identify staphylococci, such as the detection of enterotoxin production, base ratio analysis, cell wall analysis, phage typing, and serology, is discussed. The following procedures are recommended for routine use: Idnetification of Staphylococcus sp. (clinical laboratories): microscopic observation, catalase activity, coagulase production, lysostaphin sensitivity, and (optional) facultative growth in thioglycolate medium. Identification of Staphylococcus aureus (food laboratories): microscopic observation, catalase activity, coagulase production, thermonuclease production, and (optional) lysostaphin sensitivity.

Glycerol Ester Hydrolase Activity of Microbacterium thermosphactum

Microbacterium thermosphactum possesses a significant glycerol ester hydrolase (lipase, EC 3.1.1.3) activity and a weak but definite carboxylic ester hydrolase (esterase, EC 3.1.1.1) activity. Harvested whole cell preparations contained 53 units of lipase activity with tripropionin as the substrate. This activity decreased with an increasing chain length of fatty acid in the triglyceride to 13 units with trilaurin as the substrate and no activity with tripalmitin. Maximum lipase activity was found at a temperature of 35 to 37 C and at a p H of 7.1 to 7.3. Lipase activity was associated with three different protein peaks when the protein of cell-free extract was fractionated by polyacrylamide gel electrophoresis.

Isolation and characterization of a staphylococcal lipase

A number of coagulase-negative staphylococci isolated from human skin were found to produce lipase. Lipolytic activity appeared in the growth medium during the stationary phase of growth but did not appear as a result of autolysis of the cells. Maximal lipase synthesis was obtained when the medium was adjusted to pH 7.5 before inoculation. The purified enzyme hydrolyzed tributyrin and tridecanoin most actively, and a relatively high rate of hydrolysis of triolein was also noted. The optimal activity of the purified lipase was at pH 7.5. The characteristics of the concentrated crude enzyme and purified lipase were compared.

Purification and properties of a glycerol ester hydrolase (lipase) from Propionibacterium shermanii

An intracellular glycerol ester hydrolase (lipase) from Propionibacterium shermanii was recovered from cell-free extracts and purified by ammonium sulfate precipitation, gel filtration, and ion-exchange chromatography on diethylaminoethylcellulose. Maximum enzyme activity was observed at pH 7.2 and 47 C when an emulsion of tributyrin was used as substrate. The enzyme was stable between pH 5.5 and 8. Heating the enzyme solution at 45 C for 10 min resulted in a 75% decrease in activity. Maximum rate of hydrolysis of triglycerides was observed on tripropionin, followed in order by tributyrin, tricaproin, and tricaprylin. The lipase was strongly inhibited by mercury and arsenicals, but specific sulfhydryl reagents had little or no inhibiting effect on the enzyme activity. The enzyme also showed some esterase activity, but the hydrolysis of substrates in solution was small as compared to the hydrolysis of substrates in emulsion.

Lipolytic esterases in staphylococci

Staphylococci split a wide range of lipid substrates by production of an enzyme complex with two main components (i) a lipase acting optimally on fat-soluble glycerides, and (ii) an esterase acting optimally on water-soluble esters. The action is dependent upon carbon chain length, interfacial dispersion, solubility, and pH of substrate and end products. The esterase is less susceptible to organophosphorus inhibitors than mammalian esterases. There is no apparent correlation between lipolysis and markers of pathogenicity such as production of coagulase and toxin, but the possession of a flexible lipolytic mechanism might account for the persistence of staphylococci in the fatty secretions of mammalian skin.

Characterization of purified staphylococcal lipase

Purified staphylococcal lipase had an optimal pH of 8.3 for activity at 37 C, and an optimal temperature of 45 C at pH 8.0. During storage, the enzyme lost less than 10% of the activity over a period of 21 days at 4 and -23 C. The enzyme retained 93% of the activity when heated for 30 min at 50 C and was 95% destroyed in 30 min at 70 C. The purified lipase was capable of hydrolyzing a variety of natural fats and oils. However, the enzyme was three times more active on nonhydrogenated soybean oil than on hydrogenated soybean oil with an iodine value of <3.0. The enzyme was also capable of hydrolyzing fatty acids on the alpha, beta, and alpha' positions of a synthetic mixed triglyceride. In general, the presence of oxidizing agents increased the activity and the presence of reducing agents decreased the activity of the lipase enzyme.

Isolation and purification of staphylococcal lipase

An extracellular lipase was isolated from the cell-free supernatant fluid of a 24-hr culture of Staphylococcus aureus grown in Trypticase Soy Broth at 37 C with continuous agitation. The purification was achieved by precipitation with alcohol followed by differential precipitation at pH 8.6 and 4.3. Subsequent purification with Sephadex G 200 and BioGel 300 yielded a preparation which showed a 350- to 450-fold increase in specific activity over the original cell-free supernatant fluid. The purified lipase was homogeneous over a BioGel 300 column and showed a single peak on electrophoresis in a Veronal buffer (pH 8.6, Gamma/2 = 0.1). The electrophoretic mobility was -7.78 x 10(-5) cm(2) per v per sec.

A new procedure for the detection and enumeration of coagulase-positive staphylococci from frozen seafoods

A two-step procedure in which a new anaerobic liquid medium is used for a presumptive test and a solid medium (staphylococcus medium No, 110 fortified with egg yolk) incubated at 45 °C for a confirmatory test has been developed for the detection and enumeration of coagulase-positive staphylococci in frozen seafoods. The presumptive liquid medium called "Mannitol Salt Sorbic acid broth" provides specific enrichment to coagulase-positive staphylococci even in the presence of large numbers (104–105 cells) of mixed flora common to these foods. The addition of seafood material to the above medium does not affect its selective performance or its sensitivity. Also, the medium is equally efficient in recovering very low numbers of coagulase-positive staphylococcus subjected to freezing, even in the presence of the mixed flora. Incubation at 45 °C in the confirmatory step not only gives an accelerated egg yolk precipitation reaction typical of coagulase-positive staphylococci, but also enhances the specificity of the procedure.