Recent advances in the purification, characterization and structure determination of lipases

Purification and characterization of lipase produced from Bacillus cereus (PCSIR NL-37)

There is a growing trend to produce lipase from microorganisms owing to their commercial demand in various industries. Bacillus cereus has been shown to have extracellular lipase activity and high growth rates. This study explains the purification of microbial lipase to homogeneity by dialysis, precipitation and chromatography. The purified enzyme with 56kDa relative molecular mass exhibited the highest activity at 60°C (95.56U/ml) and pH 7 (124.50U/ml). The enzyme activity was highly promoted in the presence of K+ (136.17U/ml) and Zn++(133.07 U/ml), and SDS did not affect the enzyme activity, whereas in the company of triton X100 activity of lipase is maximum (23.90 U/ml). The enzyme activity was enhanced by using almond oil (120.00 U/ml) as a substrate. We deduce cheaper protocols for producing extracellular lipase via simple laboratory techniques, which could be a good insight for its production at the commercial level. Keywords: Lipase; Bacillus cereus; chromatography; enzyme activity; purification.

Characterization of Two Unique Cold-Active Lipases Derived from a Novel Deep-Sea Cold Seep Bacterium

The deep ocean microbiota has unexplored potential to provide enzymes with unique characteristics. In order to obtain cold-active lipases, bacterial strains isolated from the sediment of the deep-sea cold seep were screened, and a novel strain gcc21 exhibited a high lipase catalytic activity, even at the low temperature of 4 °C. The strain gcc21 was identified and proposed to represent a new species of Pseudomonas according to its physiological, biochemical, and genomic characteristics; it was named Pseudomonas marinensis. Two novel encoding genes for cold-active lipases (Lipase 1 and Lipase 2) were identified in the genome of strain gcc21. Genes encoding Lipase 1 and Lipase 2 were respectively cloned and overexpressed in E. coli cells, and corresponding lipases were further purified and characterized. Both Lipase 1 and Lipase 2 showed an optimal catalytic temperature at 4 °C, which is much lower than those of most reported cold-active lipases, but the activity and stability of Lipase 2 were much higher than those of Lipase 1 under different tested pHs and temperatures. In addition, Lipase 2 was more stable than Lipase 1 when treated with different metal ions, detergents, potential inhibitors, and organic solvents. In a combination of mutation and activity assays, catalytic triads of Ser, Asp, and His in Lipase 1 and Lipase 2 were demonstrated to be essential for maintaining enzyme activity. Phylogenetic analysis showed that both Lipase 1 and Lipase 2 belonged to lipase family III. Overall, our results indicate that deep-sea cold seep is a rich source for novel bacterial species that produce potentially unique cold-active enzymes.

Present status and future perspectives of breeding for buckwheat quality

Buckwheat is an important crop globally. It has been processed into cereal grain, noodles, confectionery, bread, and fermented foods for many years. Buckwheat production and processing has supported local economies and is deeply related to the culture of some regions. Buckwheat has many unique traits as a food, with a good flavor and color. In addition, buckwheat is also a healthy food because it contains bioactive compounds that have anti-oxidative, anti-hypertensive, and anti-obesity properties. Therefore, breeding of buckwheat for quality is an important issue to be addressed. Compared to other crops, there is still a lack of basic information on quality, including bioactive compounds generation and enhancement. However, some mechanisms for modifying and improving the quality of buckwheat varieties have recently been identified. Further, some varieties with improved quality have recently been developed. In this review, we summarize the issues around buckwheat quality and review the present status and future potential of buckwheat breeding for quality.

The fungal gene cluster for biosynthesis of the antibacterial agent viriditoxin

Background

Viriditoxin is one of the ‘classical’ secondary metabolites produced by fungi and that has antibacterial and other activities; however, the mechanism of its biosynthesis has remained unknown.

Results

Here, a gene cluster (vdt) responsible for viriditoxin synthesis was identified, via a bioinformatics analysis of the genomes of Paecilomyces variotii and Aspergillus viridinutans that both are viriditoxin producers. The function of the eight-membered gene cluster of P. variotii was characterized by targeted gene disruptions, revealing the roles of each gene in the synthesis of this molecule and establishing its biosynthetic pathway, which includes a Baeyer–Villiger monooxygenase catalyzed reaction. Additionally, a predicted catalytically-inactive hydrolase was identified as being required for the stereoselective biosynthesis of (M)-viriditoxin. The subcellular localizations of two proteins (VdtA and VdtG) were determined by fusing these proteins to green fluorescent protein, to establish that at least two intracellular structures are involved in the compartmentalization of the synthesis steps of this metabolite.

Conclusions

The predicted pathway for the synthesis of viriditoxin was established by a combination of genomics, bioinformatics, gene disruption and chemical analysis processes. Hence, this work reveals the basis for the synthesis of an understudied class of fungal secondary metabolites and provides a new model species for understanding the synthesis of biaryl compounds with a chiral axis.

Electronic supplementary material

The online version of this article (10.1186/s40694-019-0072-y) contains supplementary material, which is available to authorized users.

Isolation and characterization of novel lipases from a metagenomic library of the microbial community in the pitcher fluid of the carnivorous plant Nepenthes hybrida

Members of the genus Nepenthes are carnivorous plants that use the pitfall method of insect capture as a supplementary nutritional source. We extracted metagenomic DNA from the microbial community found in the pitcher fluid of Nepenthes and constructed a plasmid-based metagenomic library. An activity-based screening method enabled the isolation of two lipase genes, lip1 and lip2. Both Lip1 and Lip2 belong to a novel family or subfamily of lipases and show lipase activities in acidic conditions, such as those found in pitcher fluid. This study was conducted under the assumption that the secreted Lip1 and Lip2 were capable of enzymatic activity in the acidic pitcher fluid.

Single-step purification of lipase from Burkholderia multivorans using polypropylene matrix

Lipase from Burkholderia multivorans was purified with high yields directly from fermentation broth by a single-step purification protocol involving adsorption and desorption. The crude enzyme (lyophilized powder) from B. multivorans was loaded on Accurel (Membrana, Germany), a polypropylene matrix, using butanol as the solvent in a buffer at pH 9.0 and ambient temperature for a period of 12 h. The enzyme adsorbed onto the matrix with high specific activity (33 units mg(-1) protein). This was followed by desorption of the enzyme from the matrix using Triton X-100 as the eluent. The enzyme was finally recovered by precipitation with acetone (50%, v/v). Thus, an overall enzyme yield of 66% with a 3.0-fold purification was obtained. The purity of the enzyme was ascertained by SDS-PAGE. The phenomenon of adsorption and desorption on Accurel was studied for three more lipases, viz. Mucor meihei lipase (Sigma-Aldrich Co.), Lipolase (Novo Nordisk, Denmark) and Pseudomonas aeruginosa lipase (laboratory isolate).

Purification and characterization of lipase in buckwheat seed

To obtain basic information about enzymatic deterioration of buckwheat flour, triacylglycerol lipase (LIP; EC 3.1.1.3) was purified from buckwheat seed. The LIP consisted of two isozymes, LIP I and LIP II, and they were purified with purification folds of 60 and 143 with final specific activities of 0.108 and 0.727 mumol of fatty acid released per minute per milligram of protein at 30 degrees C using triolein as a substrate. Molecular weights were estimated to be 150 (LIP I) and 28.4 kDa (LIP I) by gel filtration and 171 (LIP I) and 26.5 kDa (LIP II) by SDS-PAGE. Optimal pHs of LIP activities were 3.0 (LIP I) and 6.0 (Lip II) using triolein as a substrate. Both LIP I and II reacted in the acidic pH range. Optimal temperatures were 30 (LIP I) and 40 degrees C (LIP II), and both LIP I and II were stable below 30 degrees C when p-nitrophenyl-laurate was used as a substrate. However, they were inactivated above 60 degrees C. On the other hand, when triolein was used as a substrate, optimal temperatures were 30 degrees C for both LIP I and II, and they retained 40% of their activity after a 4 h incubation of enzymes at 70 degrees C. LIP I and II had higher activity against triolein than monoolein or tri/monopalmitin. Most of the LIP activity was distributed in the embryo.

Purification and partial characterization of feline classical pancreatic lipase

Classical pancreatic lipase has been purified and partially characterized in many species. The objective of this project was to purify feline classical pancreatic lipase (fPL) from pancreatic tissue and partially characterize this protein. Pancreata were collected from cats (Felis catus) euthanized for unrelated research projects. Fat was removed by trimming away grossly visible fat and by extraction in organic solvents. The delipidated pancreatic extract was further purified by extracting the enzymes in a Tris-buffer containing two different protease inhibitors, benzamidine and phenylmethylsulfonyl fluoride, followed by anion-exchange, size-exclusion, and cation-exchange chromatography. Feline pancreatic lipase was successfully purified from feline pancreatic tissue. The purified product showed a single band on sodium dodecyl sulfate polyacrylamide gel electrophoresis with a molecular mass of approximately 52.5 kDa. Exact molecular mass was determined by mass spectrometry as 52.4 kDa. Approximate specific absorbance at 280 nm of fPL was 1.18 for a 1 mg/ml solution. N-terminal amino acid sequence of the first 25 amino acid residues showed the sequence Lys-Glu-Ile-?-Phe-Pro-Arg-Leu-Gly-?-Phe-Ser-Asp-Asp-Ala-Pro-Trp-Ala-Gly-Ile-Ala-Gln-Arg-Pro-Leu. This sequence showed close homology with the amino acid sequence of classical pancreatic lipase in other species.

Purification strategies for microbial lipases

Microbial lipases today occupy a place of prominence among biocatalysts owing to their ability to catalyze a wide variety of reactions in aqueous and non-aqueous media. The chemo-, regio- and enantio-specific behaviour of these enzymes has caused tremendous interest among scientists and industrialists. Lipases from a large number of bacterial, fungal and a few plant and animal sources have been purified to homogeneity. This has enabled their successful sequence determination and their three-dimensional structure leading to a better understanding of their unique structure-function relationships during various hydrolytic and synthetic reactions. This article presents a critical review of different strategies which have been employed for the purification of bacterial, yeast and fungal lipases. Since protein purification is normally done in a series of sequential steps involving a combination of different techniques, the effect of sequence of steps and the number of times each step is used is analyzed. This will prove to be of immense help while planning lipase purification. Novel purification technologies now available in this field are also reviewed.

Characterization of a highly thermostable extracellular lipase from Lactobacillus plantarum

After screening for the presence of lipase activity in lactobacilli isolated from "chouriço", a traditional Portuguese dry fermented sausage, a strain of Lactobacillus plantarum (DSMZ 12028) was chosen for extracellular lipase characterisation and purification. Proteinase K did not significantly affect lipolytic activity, as opposed to trypsin, which completely eliminated this activity. Among NaCl, Ca2+, EDTA, BSA, glycerol, Mn2+ and Mg2+, only Mn2+ and Mg2+ stimulated the lipase. Purification by gel filtration chromatography and gel electrophoresis revealed four bands, between 98 and 45 kDa, all with lipolytic activity against olive oil.

Low-temperature lipase from psychrotrophic Pseudomonas sp. strain KB700A

We have previously reported that a psychrotrophic bacterium, Pseudomonas sp. strain KB700A, which displays sigmoidal growth even at -5 degrees C, produced a lipase. A genomic DNA library of strain KB700A was introduced into Escherichia coli TG1, and screening on tributyrin-containing agar plates led to the isolation of the lipase gene. Sequence analysis revealed an open reading frame (KB-lip) consisting of 1,422 nucleotides that encoded a protein (KB-Lip) of 474 amino acids with a molecular mass of 49,924 Da. KB-Lip showed 90% identity with the lipase from Pseudomonas fluorescens and was found to be a member of Subfamily I.3 lipase. Gene expression and purification of the recombinant protein were performed. KB-Lip displayed high lipase activity in the presence of Ca2+. Addition of EDTA completely abolished lipase activity, indicating that KB-Lip was a Ca2+-dependent lipase. Addition of Mn2+ and Sr2+ also led to enhancement of lipase activity but to a much lower extent than that produced by Ca2+. The optimal pH of KB-Lip was 8 to 8.5. The addition of detergents enhanced the enzyme activity. When p-nitrophenyl esters and triglyceride substrates of various chain-lengths were examined, the lipase displayed highest activity towards C10 acyl groups. We also determined the positional specificity and found that the activity was 20-fold higher toward the 1(3) position than toward the 2 position. The optimal temperature for KB-Lip was 35 degrees C, lower than that for any previously reported Subfamily I.3 lipase. The enzyme was also thermolabile compared to these lipases. Furthermore, KB-Lip displayed higher levels of activity at low temperatures than did other enzymes from Subfamily I.3, indicating that KB-Lip has evolved to function in cold environments, in accordance with the temperature range for growth of its psychrotrophic host, strain KB700A.

Contribution of blotting techniques to the study of rapeseeds (Brassica napus L.) lipases

A recent advance in the study of plant lipases involving immunological techniques is presented. In an attempt to characterize lipases of cotyledons from germinating rapeseed seedlings and to investigate an eventual cross-reactivity with animal lipases, we have prepared anti-porcine pancreatic lipase antibodies raised in rabbit. It is shown by enzyme-linked immunosorbent assay and dot-blotting that these antibodies react with lipases in the rapeseed crude extract and in the different cellular fractions obtained by differential centrifugation. Preincubation of the antiserum with the rapeseed crude extract affects the amount of antibodies binding to the porcine pancreatic lipase. We demonstrate immunochemical cross-reactivity between rapeseed and porcine pancreatic lipase. Using the immunoblotting procedure, it is found that antibodies bind specifically to a single polypeptide with a molecular mass of about 55 kDa. Rapeseed lipase activity decreased after immunoprecipitation suggesting that antibodies were bound to some catalytic site residues. We conclude from the data obtained in this study that the two different lipase species present close similarities in amino acid sequence and antigen characteristics.

Identification of a CHO cell-elongating factor produced by Vibrio cholerae O1

Vibrio cholerae strains with all known toxin genes deleted or inactivated still cause diarrhoea in some volunteers, suggesting the presence of an unknown virulence factor or factors. Lysozyme-EDTA treated cells of JBK70, a genetically manipulated cholera toxin negative strain of Vibrio cholerae O1, biotype El Tor, release a factor that causes elongation of Chinese hamster ovary (CHO) cells. CHO cell-elongating toxin (Cef) was purified by FPLC chromatography (anion exchange; Q Sepharose High Performance) followed by 2D electrophoresis (isoelectric focusing gel, IEF; pH 3-9 and SDS-PAGE, 8-25% gradient gel). Partly purified toxin (anion exchange or IEF-eluted concentrate) caused fluid accumulation in sealed infant mice suggesting that Cef shows some properties of an enterotoxin. On SDS-PAGE (8-25%) and IEF (pH 2.5-5.0) gels, CHO cell activity was associated with a single band at 85 kDa and a pI of 3.8, respectively. A unique amino terminal sequence, XGDETNSSGASTEVVYESYIQQ, was determined by automated Edman degradation of gel-purified protein. The unique molecular mass, N-terminal sequence and activity on CHO cells indicate that this factor is not zonula occludens toxin (Zot) or accessory cholera enterotoxin (Ace) or the Hly A haemolysin. Partly purified Cef did not increase cyclic AMP or prostaglandin E(2)levels in CHO cells which suggests that its mechanism of action differs from that of cholera toxin.

Purification, characterization and thermostability of lipase from a thermophilic Bacillus sp. J33

A thermostable lipase produced by a thermophilic Bacillus sp. J33 was purified to 175-fold with 15.6% recovery by ammonium sulphate and Phenyl Sepharose column chromatography. The enzyme is a monomeric protein having molecular weight of 45 kDa. It hydrolyzes triolein at all positions. The fatty acid specificity of lipase is broad with little preference for C12 and C4. The Km and Vmax for lipase with pNP-laurate as substrate was calculated to be 2.5 mM and 0.4 microM min(-1) ml(-1) respectively. The immobilized enzyme was stable for 12 h at 60 degrees C. Polyhydric alcohols such as ethylene glycol (2.5 M), sorbitol (2.5 M) and glycerol (2.5 M) were used as thermostabilizers. Lipase acquired a remarkable stability, since no deactivation occurred at 70 degrees C for 150 min in the presence of additives.

Purification and characterization of extracellular lipases from Ophiostoma piliferum

Interest in lipases from microorganisms, animals, and plants has greatly increased in the past decade due to their applications in biotransformations and organic syntheses. We are reporting the purification and characterization of two lipases from the fungus, Ophiostoma piliferum, a saprophytic organism commonly found on wood. A major and a minor lipase have been co-purified by hydrophobic interaction chromatography on octyl sepharose FF, followed by ion exchange chromatography on Q sepharose FF. The lipases bound very tightly to octyl sepharose resulting in greater than 100-fold purification in this one step. The major lipase has a molecular weight of approximately 60 kDa, a pI of 3.79, and is glycosylated as determined by PAS staining. The minor lipase, which composes 10% of the total protein, has a pI of 3.6, and molecular weight of approximately 52 kDa and did not stain with the PAS reagent. Deglycosylation of the major lipase produced two proteins of lower molecular weight, a 55 kDa protein and a 52 kDa protein. The deglycosylated protein at 52 kDa co-migrates with the minor lipase on SDS-PAGE gels. N-terminal amino acid sequencing of the major and minor lipases indicated both lipases have the same N-termini and MALDI-TOF mass spectral analysis showed similar peptide patterns. Available data indicate that the lipases are derived from the same protein and appear to differ in their post-translational modification as evidenced by their pIs and molecular weight difference. The pH rate profile and thermal stability were determined for the purified O. piliferum lipase and were consistent with a mesophilic lipase. In aqueous solution, the lipases exhibited a higher rate of hydrolysis for p-nitrophenylbutyrate (C4) than for p-nitrophenylstearate (C18), which is an unexpected result.

Cloning and regulated expression of the Candida albicans phospholipase B (PLB1) gene

Degenerate oligonucleotides (derived from conserved regions of PLB1 genes from S. cerevisiae and other fungi) were used to amplify PLB1 homolog fragments from C. albicans and C. tropicalis by using the polymerase chain reaction. The C. albicans PLB1 fragment was then used as a probe to clone the full-length gene and to monitor PLB1 mRNA expression. The C. albicans PLB1 gene consists of a 1815-bp open reading frame encoding a putative protein of 605 amino acids. It contains the highly conserved Gly-X-Ser-X-Gly catalytic motif, found in all lipolytic enzymes, and exhibits significant homology with other fungal PLB1 gene products (approximately 63% similarity, approximately 45% identity). Blastospores and pseudohyphae expressed higher levels of PLB1 mRNA than germ-tube-forming cells. TUP1, a general transcriptional repressor, may regulate PLB1 expression in C. albicans, since PLB1 expression was the highest in tup1 delta mutants and did not vary in response to environmental stimuli. Together, these results suggest that expression of the C. albicans PLB1 gene is regulated as a function of morphogenic transition.

On the performance of a hollow-fiber bioreactor for acidolysis catalyzed by immobilized lipase

The present communication describes the chemical modification of anhydrous butterfat by interesterification with oleic acid catalyzed by a lipase of Mucor javanicus. Two reactor configurations were tested, a batch-stirred tank reactor containing suspended lipase and a batch-stirred tank reactor in combination with a hollow-fiber membrane module containing adsorbed lipase. The goal of this research was to assess the advantage of using a (hydrophobic) porous support to immobilize the lipase in attempts to engineer butterfat with increased levels of unsaturated fatty acid residues (oleic acid) at the expense of medium-to-long chain saturated fatty acids (myristic and palmitic acids). Reactions were carried out at 40 degrees C in the absence of solvent under controlled water activity, and were monitored by chromatographic assays for free fatty acids. The results obtained indicate that the rate of interesterification using the proposed reactor configuration is enhanced by a factor above 100 relative to that using suspended lipase, for the same protein mass basis. Although hydrolysis of butterfat occurred to some degree, the enzymatic process that uses the hollow-fiber reactor was technically superior to the stirred tank system. Copyright 1998 John Wiley & Sons, Inc.

Candida rugosa lipases: molecular biology and versatility in biotechnology

This review describes how the versatile Candida rugosa lipases (CRL) have extended the frontiers of biotechnology. As evidenced by the current literature, CRL claims more applications than any other biocatalyst. This review comprises a detailed discussion on the molecular biology of CRL, its versatile catalytic reactions, broad specificities and diverse immobilization strategies. It also discusses its role in the food and flavour industry, the production of ice cream and single cell protein, biocatalytic resolution of life-saving pharmaceuticals, carbohydrate esters and amino acid derivatives unobtainable by conventional chemical synthesis, potent biocide making, biosensor modulations, eco-friendly approach and bioremediation, biosurfactants in detergent making, and recently, cosmetics and perfumery.

Lipase catalyzed modification of milkfat

Decreasing consumption of high fat milk and dairy products is driving the dairy industry to seek other uses for increasing surplus of milkfat. Enzyme catalyzed modification of milkfat using lipases is receiving particular attention. This review examines lipase-mediated modification of milkfat. Especial attention is given to industrial applications of lipases for producing structured and modified milkfat for improved physical properties and digestibility, reduced caloric value, and flavor enhancement. Features associated with reactions such as hydrolysis, transesterification, alcoholysis and acidolysis are presented with emphasis on industrial feasibility, marketability and environmental concerns. Future prospects for enzyme catalyzed modification of milk fat are discussed.

Characterization of the Vibrio cholerae El Tor lipase operon lipAB and a protease gene downstream of the hly region

We have cloned and sequenced a region encoding a lipase operon and a putative, previously uncharacterized metalloprotease of Vibrio cholerae O1. These lie downstream of hlyA and hlyB, which encode the El Tor hemolysin and methyl-accepting chemotactic factor, respectively. Previous reports identified the hlyC gene downstream of hlyAB, encoding an 18.3-kDa protein. However, we now show that this open reading frame (ORF) encodes a 33-kDa protein, and since the amino acid sequence is highly homologous to the triacylglyceride-specific lipase of Pseudomonas spp., hlyC has been renamed lipA. LipA contains the highly conserved pentapeptide and catalytic triad amino acid regions of the catalytic sites of other lipases. The region downstream of lipA has been sequenced and has revealed ORFs lipB and prtV. The amino acid sequence of lipB is homologous to those of the accessory lipase proteins (lipase-specific foldase) required by Pseudomonas and various other bacterial species for the production of mature active lipase, and in agreement with this, we show that both lipA and lipB are required to restore a lipase-deficient lipA null mutant of V. cholerae. The intergenic stop codon for lipA overlaps the ribosome-binding site for lipB, and a stem-loop resembling a rho-independent terminator is present immediately downstream from lipB, suggesting that lipA and lipB form a lipase operon in V. cholerae. prtV lies downstream of lipAB but is transcribed in the opposite direction and is predicted to share the same putative transcriptional terminator with lipAB. The zinc-binding and catalytic domains conserved among many metalloproteases are present in PrtV, which is highly homologous to the immune inhibitor A (InA) metalloprotease of Bacillus thuringiensis. PrtV was visualized as approximately 102 kDa, which is consistent with the coding capacity of the gene. The genetic organization of this region suggests that it is possibly part of a pathogenicity island, encoding products capable of damaging host cells and/or involved in nutrient acquisition by V. cholerae. However, neither lipA nor prtV null mutants were attenuated in the infant mouse model, nor did they exhibit reduced colonization potential compared with wild type in competition experiments.

Molecular analysis and expression of the extracellular lipase of Aeromonas hydrophila MCC-2

The structural gene encoding the extracellular lipase of Aeromonas hydrophila MCC-2 was cloned and found to be expressed in Escherichia coli using its own promoter. When the cloned gene (lip) was expressed in E. coli minicells, an 80 kDa protein was identified. Subcellular fractionation of E. coli carrying the lip gene indicated that the Lip protein was mainly associated with the membrane fraction. Nucleotide sequence analysis revealed that the gene is 2253 bp long, coding for a 79-9 kDa protein with an estimated pl of 10.36. The deduced protein contains two putative signal peptide cleavage sites: one is a typical signal peptidase cleavage site and the other bears a strong resemblance to known lipoprotein leader sequences. Radioactivity from [3H]palmitate was incorporated into the Lip protein when expressed in E. coli. The deduced protein contains a sequence of VHFLGHSLGA which is very well conserved among lipases. It shows 67% and 65% overall identity to the amino acid sequences of lipase from A. hydrophila strains H3 and JMP636, respectively, but shows little homology to those of other lipases. The Lip protein was purified to homogeneity from both A. hydrophila and recombinant E. coli. In hydrolysis of p-nitrophenyl esters and triacylglycerols, using purified enzyme, the optimum chain lengths for the acyl moiety on the substrate were C10 to C12 for ester hydrolysis and C8 to C10 for triacylglycerol hydrolysis.

Cloning and characterization of a gene (LIP1) which encodes a lipase from the pathogenic yeast Candida albicans

Extracellular phospholipases are demonstrated virulence factors for a number of pathogenic microbes. The opportunistic pathogen Candida albicans is known to secrete phospholipases and these have been correlated with strain virulence. In an attempt to clone C. albicans genes encoding secreted phospholipases, Saccharomyces cerevisiae was transformed with a C. albicans genomic library and screened for lipolytic activity on egg-yolk agar plates, a traditional screen for phospholipase activity. Two identical clones were obtained which exhibited lipolytic activity. Nucleotide sequence analysis identified an ORF encoding a protein of 351 amino acid residues. Although no extensive homologies were identified, the sequence contained the Gly-X-Ser-X-Gly motif found in prokaryotic and eukaryotic lipases, suggesting a similar activity for the encoded protein. Indeed, culture supernatants from complemented yeast cells contained abundant hydrolytic activity against a triglyceride substrate and had no phospholipase activity. The data suggest that C. albicans, in addition to phospholipases, also has lipases. Southern blot analyses revealed that C. albicans may contain a lipase gene (LIP) family, and that a lipase gene(s) may be present in Candida parapsilosis, Candida tropicalis and Candida krusei, but not in Candida pseudotropicalis, Candida glabrata or S. cerevisiae. Northern blot analyses showed that expression of the LIP1 transcript, the cloned gene which encodes a lipase, was detected only when C. albicans was grown in media containing Tween 80, other Tweens or triglycerides as the sole carbon source, and not in Sabouraud Dextrose Broth or yeast/peptone/dextrose media. Additionally, carbohydrate supplementation inhibited LIP1 expression. Cloning this gene will allow the construction of LIP1-deficient null mutants which will be critical in determining the role of this gene in candidal virulence.

Bioreactors with immobilized lipases: state of the art

This review attempts to provide an updated compilation of studies reported in the literature pertaining to reactors containing lipases in immobilized forms, in a way that helps the reader direct a bibliographic search and develop an integrated perspective of the subject. Highlights are given to industrial applications of lipases (including control and economic considerations), as well as to methods of immobilization and configurations of reactors in which lipases are used. Features associated with immobilized lipase kinetics such as enzyme activities, adsorption properties, optimum operating conditions, and estimates of the lumped parameters in classical kinetic formulations (Michaelis-Menten model for enzyme action and first-order model for enzyme decay) are presented in the text in a systematic tabular form.

Inhibition of lipoprotein lipase induced cholesterol ester accumulation in human hepatoma HepG2 cells

It has been suggested previously that lipoprotein lipase may act as a ligand to enhance binding and uptake of lipoprotein particles. In the present study we have examined the capacity of bovine milk lipoprotein lipase to induce intracellular accumulation of triglyceride and cholesterol ester by VLDL (Sr 60-400) isolated from Type IV hypertriglyceridemic subject (HTg-VLDL) in HepG2 cells, independent of its lipolytic activity. We have also attempted to elucidate the cellular receptor mechanisms responsible for these effects. HTg-VLDL-mediated increases in intracellular triglyceride and cholesterol ester were dependent on the presence of an active lipase. Bovine milk lipoprotein lipase (LPL) increases triglyceride mass by 301% +/- 28% (P < 0.0005) and cholesterol ester mass by 176% +/- 12% (P < 0.0005). These HTg-VLDL-mediated increases in intracellular triglyceride and cholesterol ester did not occur when heat-inactivated lipase was used. Rhizopus lipase could replace LPL and cause equivalent increases in intracellular triglyceride and cholesterol ester (472% +/- 61%(P < 0.005) and 202% +/- 25% (P < 0.025) respectively vs. control). HTg-VLDL treated with LPL and reisolated also caused equivalent increases (274% +/- 18%(P < 0.01) and 177% +/- 12% (P < 0.005) for triglyceride and cholesterol ester). LDL also caused increases in intracellular cholesterol ester (189% +/- 20%(P < 0.005)), although three times more LDL cholesterol had to be added to achieve the same effect. These LDL-induced increases were effectively blocked by monoclonal antibodies directed against the B,E receptor binding domains of apo B (-97% +/- 13% (P < 0.0005) with anti-apo B 5E11 and -68% +/- 13% (P < 0.05) for anti-apo B B1B3) or by anti-B,E receptor antibodies (-77% +/- 7% (P < 0.01) antibody C7). These same antibodies had little effect on the HTg-VLDL+LPL-induced increases in cholesterol ester (+21%, +15% and -22% for 5E11, B1B3 and C7, respectively). Monoclonal anti-apo E antibodies also had no effect on LDL-mediated increases in intracellular cholesterol ester, but had a small and significant effect on VLDL-mediated increases in cholesterol ester. However, heparin, which interferes with cell surface proteoglycan interaction, was very effective at blocking HTg-VLDL-mediated increases in cholesterol ester in the presence of LPL (-86% +/- 8% P < 0.0005). Heparin was also effective in the presence of Rhizopus lipase (-79%) or lipolyzed re-isolated HTg-VLDL (-95%). These results suggest that lipoprotein lipase may enhance the uptake process beyond its role in lipolytic remodelling but does not appear to be an absolute requirement. In contrast, heparin had no effect on LDL-mediated cholesterol ester accumulation. Lactoferrin, which inhibits interaction with the low density lipoprotein receptor-related protein (LRP), was also very effective at inhibiting HTg-VLDL increases in intracellular cholesterol ester (-95% +/- 6%, P < 0.01). However, there was no effect of either heparin or lactoferrin on HTg-VLDL-mediated triglyceride accumulation. Thus cell surface heparin sulphate may facilitate intracellular lipid acquisition by providing a stabilizing bridge with the lipoproteins and enhance uptake through receptor-mediated processes such as LRP.

Fusarium polycaprolactone depolymerase is cutinase

Polycaprolactone (PCL), a synthetic polyester, is degraded by a variety of microorganisms, including some phytopathogens. Many phytopathogens secrete cutinase, a serine hydrolase that degrades cutin, the structural polymer of the plant cuticle. We compared wild-type strains and a cutinase-negative gene replacement mutant strain of Fusarium solani f. sp. pisi (D. J. Stahl and W. Schäfer, Plant Cell 4:621-629, 1992) and a wild-type strain of Fusarium moniliforme to show that Fusarium cutinase is a PCL depolymerase. The wild-type strains, but not the mutant strain, (i) degraded PCL and used it as a source of carbon and energy, (ii) showed induction of secreted PCL depolymerase and an esterase activity of cutinase when grown in the presence of cutin, and (iii) showed induction of PCL depolymerase and an esterase activity of cutinase when grown in the presence of a hydrolysate of PCL, which contains PCL oligomers that are structurally similar to the natural inducers of cutinase. These results together with other details of regulation and conditions for optimal enzyme activity indicate that the Fusarium PCL depolymerase, required for degradation and utilization of PCL, is cutinase.

Bacterial lipases

Many different bacterial species produce lipases which hydrolyze esters of glycerol with preferably long-chain fatty acids. They act at the interface generated by a hydrophobic lipid substrate in a hydrophilic aqueous medium. A characteristic property of lipases is called interfacial activation, meaning a sharp increase in lipase activity observed when the substrate starts to form an emulsion, thereby presenting to the enzyme an interfacial area. As a consequence, the kinetics of a lipase reaction do not follow the classical Michaelis-Menten model. With only a few exceptions, bacterial lipases are able to completely hydrolyze a triacylglycerol substrate although a certain preference for primary ester bonds has been observed. Numerous lipase assay methods are available using coloured or fluorescent substrates which allow spectroscopic and fluorimetric detection of lipase activity. Another important assay is based on titration of fatty acids released from the substrate. Newly developed methods allow to exactly determine lipase activity via controlled surface pressure or by means of a computer-controlled oil drop tensiometer. The synthesis and secretion of lipases by bacteria is influenced by a variety of environmental factors like ions, carbon sources, or presence of non-metabolizable polysaccharides. The secretion pathway is known for Pseudomonas lipases with P. aeruginosa lipase using a two-step mechanism and P. fluorescens lipase using a one-step mechanism. Additionally, some Pseudomonas lipases need specific chaperone-like proteins assisting their correct folding in the periplasm. These lipase-specific foldases (Lif-proteins) which show a high degree of amino acid sequence homology among different Pseudomonas species are coded for by genes located immediately downstream the lipase structural genes. A comparison of different bacterial lipases on the basis of primary structure revealed only very limited sequence homology. However, determination of the three-dimensional structure of the P. glumae lipase indicated that at least some of the bacterial lipases will presumably reveal a conserved folding pattern called the alpha/beta-hydrolase fold, which has been described for other microbial and human lipases. The catalytic site of lipases is buried inside the protein and contains a serine-protease-like catalytic triad consisting of the amino acids serine, histidine, and aspartate (or glutamate). The Ser-residue is located in a strictly conserved beta-epsilon Ser-alpha motif. The active site is covered by a lid-like alpha-helical structure which moves away upon contact of the lipase with its substrate, thereby exposing hydrophobic residues at the protein's surface mediating the contact between protein and substrate.(ABSTRACT TRUNCATED AT 400 WORDS)

Screening, purification and properties of a thermophilic lipase from Bacillus thermocatenulatus

By screening of 15 thermophilic Bacillus strains, five strains exhibiting lipase activity were found. Among these the strain Bacillus thermocatenulatus (DSM 730) produced the highest lipase activity. The lipase proved to be inducible and extracellular and was purified 67-fold to homogenous state by hexane extraction, methanol precipitation and ion-exchange chromatography on Q-Sepharose. The molecular weight of the lipase determined by SDS-PAGE is 16 kDa. However, the lipase forms very large aggregates (> 750 kDa) as observed after native PAGE, which makes handling of the lipase very difficult. The lipase binds almost irreversibly on different chromatography matrices, e.g., Amberlite and Serolite, and is very stable in the immobilised form. The N-terminal sequence consists of 53% apolar amino acids and shows no significant homology towards other known lipase sequences. Maximum activity was found at pH 7.5-8.0 and 60-70 degrees C with pNPP and olive oil as substrates.

Purification and characterization of Pseudomonas fluorescens SIK W1 lipase expressed in Escherichia coli

Pseudomonas fluorescens SIK W1 lipase was expressed as a form of inclusion bodies in Escherichia coli, which was equivalent to 46% of total cell protein. The inclusion bodies isolated from other cell components were solubilized in the buffer containing 8 M urea and then refolded by diluting urea. The lipase with active conformation was purified by hydrophobic interaction chromatography, gel filtration, anion-exchange chromatography and hydroxyapatite chromatography from the refolded sample. By these purification steps, a single band for active lipase was detected on non-reducing SDS-PAGE and 10-fold purification was attained on the basis of specific activity. Specific activity of the purified lipase toward olive oil emulsion was found to be 7395 units per mg protein. The optimum pH and temperature of the lipase were pH 8.5 and 45-55 degrees C, respectively. The lipase showed higher lipolytic activity toward tricaproin (C6) and tricaprylin (C8) among the triacylglycerols examined and preferentially hydrolyzed ester bond of 1- and 3-position of triolein. Lipase activity was greatly increased by approx. 6-fold and stability for pH was shifted to alkaline pH by Ca2+ ion. The lipase was inhibited by Hg2+, Ag2+, p-chloromercuribenzoate, diethylpyrocarbonate and sodium dodecyl sulfate.

Phase variation in Xenorhabdus luminescens: cloning and sequencing of the lipase gene and analysis of its expression in primary and secondary phases of the bacterium

The phenomenon of phase variation in the insect-pathogenic bacterium Xenorhabdus luminescens was investigated. Differential activity of the lipase enzyme (EC 3.1.1.3) was observed between the two phases of the bacteria. The enzyme was found to be secreted into the culture medium, and about five to six times greater specific activity was secreted by the primary phase than by the secondary form. The lipase gene (lip-1) was cloned and sequenced. The data imply that there is only a single Tween 80-utilizing lipase gene in X. luminescens K122. The sequence revealed a translation product of 645 amino acids, from which a hydrophobic leader sequence of 24 amino acids is removed during processing. The structure of the gene was shown to be the same in the primary and secondary forms of X. luminescens. In addition, transcription was found to start at the same position, 169 bp upstream of the translation initiation codon, in the two forms of the bacteria. Equal amounts of lipase RNA accumulated in the two forms, and at least as much lipase protein was secreted by the secondary form as by the primary. This suggests that the difference in specific activity between the enzymes secreted by the two phases probably arises from a posttranslational type of regulation.

Cloning and analysis of Candida cylindracea lipase sequences

Lipases (Lip) hydrolyze triglycerides into fatty acids and glycerol. Lip produced by the yeast Candida cylindracea are encoded by multiple genomic sequences. We report the molecular cloning and characterization of three genes from this family. They encode putative mature 57-kDa proteins of 534 amino acids (aa). To date, five Lip-encoding genomic sequences from C. cylindracea have been characterized in our laboratory. The five deduced aa sequences share an overall homology of 80%. These sequences have been aligned with each other and with those of homologous enzymes, the Lip from the mould Geotrichum candidum and the acetylcholinesterase from Torpedo californica, whose three-dimensional structures have been solved by X-ray analysis. The C. cylindracea Lip appear to have a structural organization similar to that described for both enzymes.

News from the interface: the molecular structures of triacylglyceride lipases

Neutral lipases constitute one of the most ubiquitous and diverse families of enzymes. The recently solved crystal structures of three lipases show that enzymatic hydrolysis occurs with the assistance of a catalytic triad, which is structurally reminiscent of serine proteinases. However, these lipases only become active at the oil-water interface through a conformational change that exposes the active centre of the enzyme.

Homology-derived three-dimensional structure prediction of Candida cylindracea lipase

We propose a structural model of Candida cylindracea lipase (CCL) based on the reported X-ray structure of the highly homologous Geotrichum candidum lipase (GCL). The network of interactions around the active site, the salt and disulfide bridge pattern is conserved in the proposed structure. Functional, structural and evolutionary aspects of the peculiar usage of CTG codons by C. cylindracea ATCC 14830 are discussed.