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PubMed1990

[The characterization of microbial lipases. 1. The determination of lipase activity].

In the selection of an appropriate method for activity determination of lipases existing technical equipment, kind of enzymes, number of samples investigated (e.g. in routine analysis), and expected sensitivity range have to be taken into account. Titrimetric methods and above all copper salt methods with their high detection sensitivity are the most suitable procedures for activity determination of lipases used in laboratories and institutions without equipment for radiochemical analysis.

Bacteria↗
PubMed1991

[The characterization of microbial lipases. 2. The determination of lipase specificity].

Types of lipase specificity are as follows: Positional specificity; fatty acid specificity; stereospecificity; substrate specificity (different rates of lipolysis of different glyceride classes. The acylglycerol used for determination of lipase specificity must be so structured, that specificities are not confused and unambiguous results are obtained. Different substrates and methods for detection of specificity are reviewed and advantages and disadvantages are discussed. Positional specificity can be determined with synthetic dialkylacylglycerols and 2,3-dioleoyl butanediol. Stereospecificity can be detected with enantiomeric dialkylacylglycerols or diacylalkylglycerols.

Amino Acid Sequence↗
PubMed1989

Determination of triacylglycerol lipase activity using carbon-13-labeled triacylglycerols and nuclear magnetic resonance spectroscopy: evidence that hepatic lipase hydrolyzes medium-chain triacylglycerols.

Triacylglycerol lipase activity was studied using glycerol [1-13C]trioctanoate mixed with postheparin rat plasma. 13C NMR spectroscopy demonstrated triacylglycerol hydrolysis into free fatty acids with no difference at the 1,3 or 2 glycerol positions. There was no inhibition by high sodium concentration, consistent with lipase of hepatic origin.

Animals↗
PubMed1995

Overexpression of human lipoprotein lipase increases hormone-sensitive lipase activity in adipose tissue of mice.

An elevation of lipoprotein lipase (LPL) activity in adipose tissue is considered a possible cause of obesity. However, transgenic mice that overexpress the human LPL gene showed no increase in fat deposition as compared with controls. In the present study, we investigated effects of LPL on fat accumulation. Respiratory quotients and uptake of [3H] triolein by tissues (white and brown adipose tissue, and skeletal muscles) did not differ significantly for transgenic and non-transgenic mice. The mRNA levels of hormone-sensitive lipase (HSL) and HSL activity in adipose tissue during feeding were higher in LPL transgenic mice than in controls. Results suggest that the overexpression of LPL does not induce obesity by enhancing the hydrolysis of triglycerides in adipose tissue.

Adipose Tissue↗
PubMed1998

Pancreatic lipase-related protein type 1: a double mutation restores a significant lipase activity.

Besides the active pancreatic lipase (PL) which plays a major role in dietary fat digestion, the presence of a pancreatic lipase related protein 1 (PLRP1) displaying a very low lipolytic activity has been reported in vertebrates. It has been suggested that the reduced lipolytic activity of PLRP1 results from specific features of the N-terminal domain of the protein. Therefore, based on sequence comparison between PL and PLRP1 and modelling experiments, several residues located in the vicinity of the active site pocket of both enzymes have been mutated. In this paper, we report that, as regards to PL, two substitutions in positions 179 and 181 in PLRP1 account for the very low lipolytic activity of the protein. Indeed, substituting these residues (V179 and A181) in PLRP1 for those found in PL (A179 and P181), restores a significant lipolytic activity for PLRP1.

Animals↗
PubMed1985

A colorimetric assay of pancreatic lipase: rapid detection of lipase and colipase separated by gel filtration.

A rapid assay for pancreatic lipase (E.C., glycerol-ester hydrolase 3.1.1.3) is described. The assay is based on the color change of a pH indicator as butyric acid is released from the substrate tributyrin. A mixture made with tributyrin and the water soluble components of the assay is ideally suited for use as a rapid test as, for example, when assaying chromatography fractions. Quantitative data can be obtained by measuring the disappearance of absorbance at 557 nm versus a blank reaction. The assay has been used in the rapid preparation of colipase-free lipase and colipase.

Chromatography, Gel↗
PubMed2005

Rosiglitazone up-regulates lipoprotein lipase, hormone-sensitive lipase and uncoupling protein-1, and down-regulates insulin-induced fatty acid synthase gene expression in brown adipocytes of Wistar rats.

AIMS/HYPOTHESIS: Although thiazolidinediones are now widely used to treat type 2 diabetes, their mechanism of action remains largely unknown. They are agonists for the transcription factor PPARgamma, and in addition to their insulin-sensitising effects, they can promote adipogenesis and control gene expression in adipose tissues. We have explored the effect of rosiglitazone on insulin-mediated induction of pivotal genes involved in lipid metabolism and thermogenesis in brown fat. The genes studied were: (1) lipoprotein lipase (lpl), which is involved in lipid uptake; (2) hormone-sensitive lipase (hsl), which mobilises fatty acids from stored triglycerides; (3) fatty acid synthase (fas), which regulates de novo lipogenesis; and (4) the uncoupling proteins (ucp) 1 and 3, which control thermogenesis. METHODS: We used fetal rat primary brown adipocytes cultured with insulin, rosiglitazone or both combined. Then, we studied gene expression by northern and western blotting, as well as 'run-on' and gel-shift assays to identify binding of potential transcription factors to the fas promoter. RESULTS: Exposure to rosiglitazone for 24 h induced ucp-1, lpl and hsl gene expression and when rosiglitazone was combined with insulin a synergistic effect on lpl and ucp-3 mRNA expression was produced. These effects were consistent with increased LPL and HSL activities as well as respiration rates, mainly in response to exogenous palmitate. In contrast, treatment with rosiglitazone did not alter FAS mRNA basal levels but prevented the induction elicited by insulin in a time- and dose-dependent manner. Correspondingly diminished FAS protein levels and activity, as well as cellular lipid content, were observed, indicating an antilipogenic action of rosiglitazone in brown adipocytes. Furthermore, rosiglitazone impaired insulin increase in the FAS transcription rate by antagonising insulin-induced binding of upstream stimulatory factors to the E-box consensus sequence in the FAS promoter and insulin-induced binding of activating protein-1. CONCLUSIONS/INTERPRETATION: Rosiglitazone prevents insulin-induced up-regulation of the main lipogenic enzyme but increases the expression of those enzymes involved in lipid uptake and mobilisation, favouring fatty acid utilisation through uncoupled respiration.

Adipocytes↗
PubMed1976

Stereospecificity of lipases. Enzymatic hydrolysis of enantiomeric alkyldiacyl- and dialkylacylglycerols by lipoprotein lipase.

Lipoprotein lipase from dialyzed and lyophilized bovine skim milk hydrolyses specifically the ester in position 1 of triacylglycerols and of enantiomeric alkyldiacylglycerols. No such specificity could be observed when enantiomeric dialkylacylglycerols were used as substrates since hydrolysis in positions 1 and 3 occurred at the same rate. Dialkylacylglycerols are, therefore, unsuitable as model substrates for the assay of the stereospecificity of lipases.

Animals↗
PubMed1982

Measurement of the binding of human colipase to human lipase and lipase substrates.

Equilibrium partition in an aqueous two-phase system was the method used for quantitative determinations of the binding between human colipase and human lipase and three triacylglycerol substrates: Intralipid tributyrin and triolein. The measurements were performed in a dextran/polyethyleneglycol system at pH 7.0 in the presence of 2 mM sodium taurodeoxycholate and 150 mM NaCL. The binding of colipase to lipase had a dissociation constant Kd = 4.8 . 10(-8) M. The dissociation constants for the binding of colipase to Intralipid, tributyrin and triolein were found to be 2.10(-7) M, 4.8 . 10(-8) M and 6.2 . 10(-8) M, respectively.

Colipases↗
PubMed1991

Effect of pancreatic phospholipase A2 and gastric lipase on the action of pancreatic carboxyl ester lipase against lipid substrates in vitro.

Preincubation of a triolein/phospholipid/cholesteryl oleate-emulsion in vitro with either pancreatic phospholipase A2 (PLA2) or gastric lipase (GL) resulted in hydrolysis (measured by pH-stat-titration) of cholesteryl [3H]oleate only after human pancreatic carboxyl ester lipase (CEL) was added to the system. No appreciable hydrolysis was observed when CEL was added alone. Consequently, a concerted action either of PLA2 and CEL or of GL and CEL made the substrate cholesteryl oleate available for hydrolysis by CEL. This was the case when cholesteryl oleate was solubilised in a phospholipid-stabilised triglyceride emulsion, which is the physico-chemical form in which the major part of dietary cholesteryl esters are presented to the gastro-intestinal tract of man.

Carboxylesterase↗
PubMed1990

A new approach to determine the stereospecificity in lipase catalysed hydrolysis using circular dichroism (CD): lipases produce optically active diglycerides from achiral triglycerides.

We describe a sensitive CD method for determining the stereospecificity in lipase (E.C.3.1.1.3) catalysed hydrolysis of triacyl glycerols into diacyl glycerols. The diglycerols were converted to chiral tert-butyldimethylsilylated 1,2- or 2,3-di-O-benzoyl-sn-glycerol (5 or 5'), and their CD was measured. This approach showed for the first time that lipases produce optically active diacyl glycerides from achiral tripalmitin and tribenzoyl glyceride with a variable extent of enantioselectivity depending on the acyl groups and the enzymes.

Benzyl Alcohols↗
PubMed1992

Annexin II inhibits calcium-dependent phospholipase A1 and lysophospholipase but not triacyl glycerol lipase activities of rat liver hepatic lipase.

A member of the annexin family (the heterotetrameric annexin II2p11(2) complex purified from porcine intestinal epithelium) was tested for its ability to affect different calcium-dependent intrinsic lipolytic activities of rat liver hepatic lipase (HL). Whereas annexin II in the presence of calcium failed to interfere with HL triacyl glycerol lipase (EC 3.1.1.3) activity, it inhibited HL phospholipase A1 (EC 3.1.1.32) and lysophospholipase (EC 3.1.1.5) activities. Inhibition could be overcome by increasing the substrate concentration. Under phospholipase A1 assay conditions, annexin II did not bind to the purified HL enzyme. These results therefore suggest that only inhibitor/substrate interactions lead to inhibition of HL phospholipase A1 and lysophospholipase activities, an obviously general mechanism of phospholipase inhibition by annexins. Possible implications of HL inhibition in vivo by annexins are discussed.

Animals↗
PubMed1976

Clearing factor lipase (lipoprotein lipase) activator. A method for the measurement of the net activating ability of human sera.

The hydrolysis of an emulsified triglyceride substrate by clearing factor lipase (lipoprotein lipase) normally requires the presence of particular activating polypeptide species. These are present in serum, together with other inhibitory species, as part of the serum lipoproteins. The paper describes a method whereby the net activating ability of individual human sera may be measured routinely. In a normal population, this activating ability is shown to be correlated positively with the fasting serum triglyceride concentration. As the fasting triglyceride concentration increases, there is a rise in the proportion of the total activating ability that is associated with the very low density lipoproteins. A dietary fat load does not raise the total activating ability but does increase the proportion of the total that is associated with the serum lipoproteins of lowest density.

Animals↗
PubMed1995

Coordinated regulation of hormone-sensitive lipase and lipoprotein lipase in human adipose tissue in vivo: implications for the control of fat storage and fat mobilization.

The enzymes lipoprotein lipase (LPL, EC 3.1.1.34) and hormone-sensitive lipase (HSL, EC 3.1.1.3) apparently catalyze opposing functions in white adipose tissue: the former is concerned with fat storage, the latter with fat mobilization. We have studied their regulation in vivo in normal subjects in the postabsorptive state and after eating meals of different compositions, by measurement of arteriovenous concentration differences for triacylglycerol, non-esterified fatty acids and glycerol across a subcutaneous adipose depot. The two enzymes are regulated in a broadly reciprocal manner: in the overnight-fasted state, HSL is more active, but after a meal HSL is suppressed whilst LPL is activated. The movement of fatty acids in and out of adipose tissue appears to be driven by concentration gradients generated by regulation of these two enzymes, and also by activation, in the postprandial period, of the process of fatty acid esterification. The results show some interesting and perhaps unexpected features of metabolic regulation. Of the fatty acids generated by the action of LPL on circulating TAG, a large proportion is released directly into the venous plasma: close to 100% in the overnight-fasted state, and 50% or more at the peak of LPL action after a meal, making what appear reasonable assumptions. We suggest that this apparent 'inefficiency' of fat storage reflects the energetic cost of maintaining precise control over such a fundamental process. Although LPL is usually thought of as the enzyme regulating fat deposition, in fact the fatty acids and glycerol it releases from circulating TAG represent a substantial proportion of those released from adipose tissue, especially in the postprandial state. In addition, although HSL is considered the enzyme responsible for fat mobilization, suppression of its activity is essential to normal regulation of fat deposition. Thus, fat storage and fat mobilization during normal daily life are controlled by coordinated regulation of a number of enzymatic processes in white adipose tissue.

Adipose Tissue↗
PubMed1989

Expression of lipoprotein lipase gene in combined lipase deficiency.

The expression of the gene for lipoprotein lipase (LPL) was studied in brown adipose tissue and the liver of combined lipase deficient (cld/cld) and unaffected mice. The mRNA specific for LPL was detected in both animals. Although the size of LPL mRNA in cld mice was similar to that of unaffected mice, the mRNA concentration in affected animals was higher than in unaffected animals. We also studied the LPL gene mutation in cld mice by Southern blot analysis. No restriction fragment length polymorphisms were observed after digestion with 16 endonucleases. These data indicate that there is no gene insertion or deletion, but do not exclude the possibility of point mutation in the LPL structural gene. However, the present results agree with the hypothesis that the genetic defect in cld is not due to a mutation in the LPL structural gene, but instead involves the defective post-translational processing of LPL or defective cellular function affecting transport and secretion of this enzyme group.

Animals↗
PubMed1994

Sequence of the Streptomyces albus G lipase-encoding gene reveals the presence of a prokaryotic lipase family.

An extracellular lipase (Lip)-encoding gene from Streptomyces albus G has been cloned and sequenced. It encodes a Lip with 82% sequence identity to another previously cloned Lip from a Streptomyces species not closely related. These two sequences can be aligned with 33% identity to the sequence of Lip1 from the antarctic psychrotroph Moraxella TA144 [G. Feller et al., Nucleic Acids Res. 18 (1990) 6431]. An alignment of the three sequences revealed amino-acid substitutions which might be responsible for the greater thermal stability of the Streptomyces lipases. The presence of this lip gene family in several members of the Streptomyces genus was also shown.

Amino Acid Sequence↗
PubMed2006

Monitoring lipase-catalyzed methanolysis of sunflower oil by reversed-phase high-performance liquid chromatography: elucidation of the mechanisms of lipases.

Reversed-phase high-performance liquid chromatography (RP-HPLC) with UV detection at 210 nm was used to monitor the formation of the major compounds during the lipase-catalyzed transesterification reaction of sunflower oil with methanol. Individual triacylglycerols, diacylglycerols, monoacylglycerols as well as fatty acids and their corresponding methyl esters were separated using acetonitrile/acetone as a mobile phase and a combined linear gradient-isocratic-step gradient-isocratic elution procedure. Another relatively short method consisting of a linear gradient elution followed by an isocratic elution gave similar results, yet with lower resolution. HPLC/mass spectrometry with an ion trap analyzer and atmospheric pressure chemical ionization source was used for the identification of the individual compounds. Individual calibration curves obtained with UV detection at 210 nm were found to be of use for quantitative analyses of double-bond containing methyl esters and acylglycerols. The use of the RP-HPLC methods in the elucidation of the mechanisms of three immobilized lipases, namely Lipozyme TL IM, Lipozyme RM IM and Novozym 435, in biodiesel production was described.

Chromatography, High Pressure Liquid↗