Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “LIPASE”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 235 records · Page 13Linked to original sources
PubMed1983

Dyslipoproteinaemia in hypothyroidism of pituitary origin: effects of L-thyroxine substitution on lipoprotein lipase, hepatic lipase, and on plasma lipoproteins.

We have studied the effects of L-thyroxine substitution on lipoprotein concentrations, on the activities of lipoprotein lipase (LPL) and hepatic lipase (HL), and on the elimination rate of exogenous triglyceride in a homogeneous group of patients with hypothyroidism of pituitary origin. All were deficient of sex hormones but not of corticosteroids during the observation period. Before treatment total plasma cholesterol, LDL cholesterol, and triglyceride levels were significantly higher than in a euthyroid control group but not as high as in patients with overt primary hypothyroidism. The activities of LPL and HL were also intermediate between those of euthyroid and overt primary hypothyroid subjects, and there was a significant reduction of the elimination rate of exogenous triglyceride. No changes were found for HDL cholesterol levels. When the patients with secondary hypothyroidism were compared to patients with primary hypothyroidism, matched for thyroid function levels, age, sex, and weight, there were no differences with regard to plasma lipoprotein concentrations or post-heparin lipase activities. In 3 patients with secondary hypothyroidism the lipoprotein profiles were studied by zonal ultracentrifugation and found to agree well with changes observed in primary hypothyroidism. L-thyroxine substitution produced a normalization of lipase activities and lipoprotein concentrations in patients with secondary hypothyroidism. We conclude that there are no fundamental differences in the disturbances of the lipoprotein metabolism in primary and secondary forms of hypothyroidism.

Adolescent↗
PubMed1991

Effects of gene mutations in lipoprotein and hepatic lipases as interpreted by a molecular model of the pancreatic triglyceride lipase.

A molecular model of human pancreatic lipase (Winkler, F. K., D'Arcy, A., and Hunziker, W. (1990) Nature 343, 771-774) is used to explain the possible structural effects of the amino acid mutations identified to date in the human lipoprotein and hepatic lipase genes. A sequence homology profile was used to evaluate the alignment of the amino acid sequences of all three lipolytic enzymes (Kirchgessner, T. G., Chuat, J.-C., Heinzmann, C., Etienne, J., Guilhot, S., Svenson, K., Ameis, D., Pilon, C., D'Auriol, L., Andalibi, A., Schotz, M. C., Galibert, F., and Lusis, A. J. (1989) Proc. Natl. Acad. Sci. U. S. A. 86, 9647-9651) with respect to the secondary structure elements identified in the pancreatic lipase. As expected, maximum homology is observed in internal regions namely the hydrophobic strands of the central beta-pleated sheet. This observation strongly supports the hypothesis that all three molecules exhibit a very similar three-dimensional structure, particularly in the N-terminal catalytic domain. There is considerable variation in some of the surface loops connecting the individual strands, whereas others are conserved. It is hypothesized that the most conserved loops located around the active site are responsible for the catalytic function (similar for all three enzymes), whereas those that markedly differ are involved in the regulation at the molecular level, namely the binding of colipase (pancreatic enzyme) and apolipoprotein CII (lipoprotein lipase). The currently available library of hepatic and lipoprotein gene mutations seems to indicate that the majority of mutants disrupt the folding of the polypeptide chain, rather than affect specific constellations in and around the catalytic site or regulatory loops.

Amino Acid Sequence↗
PubMed1990

A sandwich-enzyme immunoassay for the quantification of lipoprotein lipase and hepatic triglyceride lipase in human postheparin plasma using monoclonal antibodies to the corresponding enzymes.

We have developed a sandwich-enzyme immunoassay (EIA) for the quantification of lipoprotein lipase (LPL) and hepatic triglyceride lipase (HTGL) in human postheparin plasma (PHP) using monoclonal antibodies (MAbs) directed against the corresponding enzymes purified from human PHP. The sandwich-EIA for LPL was performed by using the combination of two distinct types of anti-LPL MAbs that recognize different epitopes on the LPL molecule. The immunoreactive mass of LPL was specifically measured using a beta-galactosidase-labeled anti-LPL MAb as an enzyme-linked MAb, an anti-LPL MAb linked with the bacterial cell wall as an insolubilized MAb, and purified human PHP-LPL as a standard. The sandwich-EIA for HTGL was carried out by using two distinct anti-HTGL MAbs that recognize different epitopes on HTGL. The limit of detection was 20 ng/ml for LPL and 60 ng/ml for HTGL. Each method yielded a coefficient of variation of less than 6% in intra- and inter-assays, and a high concentration of triglyceride did not interfere with the assays. The average recovery of purified human PHP-LPL and -HTGL added to human PHP samples was 98.8% and 97.5%, respectively. The immunoreactive masses of LPL and HTGL in PHP samples, obtained at a heparin dose of 30 IU/kg, from 34 normolipidemic and 20 hypertriglyceridemic subjects were quantified by the sandwich-EIA. To assess the reliability of the measured mass values, they were compared with the corresponding enzyme activities measured by selective immunoinactivation assay using rabbit anti-human PHP-LPL and -HTGL polyclonal antisera. Both assay methods yielded a highly significant correlation in either normolipidemic (r = 0.945 for LPL; r = 0.932 for HTGL) or hypertriglyceridemic subjects (r = 0.989 for LPL; r = 0.954 for HTGL). The normal mean (+/- SD) level of lipoprotein lipase mass and activity in postheparin plasma was 223 +/- 66 ng/ml and 10.1 +/- 2.9 mumol/h per ml, and that of hepatic triglyceride lipase mass and activity was 1456 +/- 469 ng/ml and 26.4 +/- 8.7 mumol/h per ml, respectively. The present sandwich-enzyme immunoassay methods make it possible to study the molecular nature of LPL and HTGL in PHP from patients with either primary or secondary hyperlipoproteinemia.

Adult↗
PubMed1989

The fatty liver dystrophy (fld) mutation. A new mutant mouse with a developmental abnormality in triglyceride metabolism and associated tissue-specific defects in lipoprotein lipase and hepatic lipase activities.

An autosomal recessive mutation, termed fatty liver dystrophy (fld), can be identified in neonatal mice by their enlarged and fatty liver (Sweet, H. O., Birkenmeier, E. H., and Davisson, M. T. (1988) Mouse News Letter 81, 69). We have examined the underlying metabolic abnormalities in fld/fld mice from postnatal days 3-40. Serum and hepatic triglyceride levels were elevated 5-fold in suckling fld/fld mice compared to their +/? littermates but abruptly resolved at the suckling/weaning transition. Blot hybridization analysis of liver and intestinal RNAs revealed a liver-specific increase in apolipoprotein (apo) A-IV and C-II mRNA concentrations (100- and 6-fold, respectively) that was limited to the suckling and early weaning stages in fld/fld mice. Resolution of these differences during the weaning period could not be delayed by prolonging suckling to the 20th postnatal day nor could the mutant phenotype be elicited in young adult animals with a high fat diet. Lipoprotein lipase (LPL) activity was reduced 16-fold in the white adipose tissue of fld/fld mice until the onset of weaning. Heart activity was decreased less than 2-fold, but there were no deficits in brown adipose tissue or liver. Hepatic lipase (HL) mRNA levels and activity were significantly reduced in fld/fld livers and sera, respectively, during the suckling period. Mapping studies show the fld locus to be distinct from loci encoding LPL, HL, and apoA-IV, and those responsible for the combined lipase deficiencies in cld/cld and W/Wv mice. These data suggest that the fld mutation is associated with developmentally programmed tissue-specific defects in the neonatal expression of LPL and HL activities and provide evidence for a new regulatory locus which affects these lipase activities. This mutation could serve as a useful model for (i) analyzing the homeostatic mechanisms controlling lipid metabolism in newborn mice and (ii) understanding and treating certain inborn errors in human triglyceride metabolism.

Adipose Tissue↗
PubMed1989

Lipoprotein lipase and hepatic lipase mRNA tissue specific expression, developmental regulation, and evolution.

Lipoprotein lipase (LPL) and hepatic lipase (HL) enzyme activities were previously reported to be regulated during development, but the underlying molecular events are unknown. In addition, little is known about LPL evolution. We cloned and sequenced a complete mouse LPL cDNA. Comparison of sequences from mouse, human, bovine, and guinea pig cDNAs indicated that the rates of evolution of mouse, human, and bovine LPL are quite low, but guinea pig LPL has evolved several times faster than the others. 32P-Labeled mouse LPL and rat HL cDNAs were used to study lipase mRNA tissue distribution and developmental regulation in the rat. Northern gel analysis revealed the presence of a single 1.87 kb HL mRNA species in liver, but not in other tissues including adrenal and ovary. A single 4.0 kb LPL mRNA species was detected in epididymal fat, heart, psoas muscle, lactating mammary gland, adrenal, lung, and ovary, but not in adult kidney, liver, intestine, or brain. Quantitative slot-blot hybridization analysis demonstrated the following relative amounts of LPL mRNA in rat tissues: adipose, 100%; heart, 94%; adrenal, 6.6%; muscle, 3.8%; lung, 3.0%; kidney, 0%; adult liver, 0%. The same quantitative analysis was used to study lipase mRNA levels during development. There was little postnatal variation in LPL mRNA in adipose tissue; maximal levels were detected at the earliest time points studied for both inguinal and epididymal fat. In heart, however, LPL mRNA was detected at low levels 6 days before birth and increased 278-fold as the animals grew to adulthood.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Lipoprotein lipase and hepatic lipase: the role of asparagine-linked glycosylation in the expression of a functional enzyme.

Lipoprotein lipase (LPL) and hepatic lipase (HL) share two conserved asparagine-linked glycosylation sites, located at the amino- and carboxy-terminal domains of the protein. Human HL contains two additional sites, preceding each conserved site by 36 and 35 amino acids, respectively. The utilization of these sites for glycan-binding and the role of each glycan chain for the catalytic function of human LPL, rat HL, and human HL was investigated. To accomplish this aim, potential Asn glycosylation sites were changed to Gln by site-directed mutagenesis and the resulting constructs were expressed in a mammalian (COS) cell system. We demonstrate the following. 1) All potential glycosylation sites in human LPL, rat HL, and human HL are utilized. 2) Lack of glycosylation at the two non-conserved sites in human HL has no effect on enzyme expression. 3) Glycosylation at the conserved Asn sites in the N-terminal domain of LPL and HL is required for the synthesis of a fully active and secreted lipase. While this is an absolute requirement for LPL, a portion (approximately 25%) of HL molecules lacking glycosylation at this essential site still becomes active and secreted. However, the simultaneous elimination of both glycosylation sites at the N-terminal domain of human HL results in the virtual abolishment of enzymatic activity and secretion. 4) Glycosylation at the conserved sites in the C-terminal domain is not essential for the expression of active lipases. 5) Eliminating all glycosylation sites in LPL and HL results in the synthesis of inactive enzymes that are retained intracellularly; however, a small portion (2%) of unglycosylated rat HL was active and secreted. We conclude that glycosylation overall plays an important role in the formation of functional LPL and HL.

Animals↗
PubMed1994

High density lipoproteins with differing apolipoproteins: relationships to postprandial lipemia, cholesteryl ester transfer protein, and activities of lipoprotein lipase, hepatic lipase, and lecithin: cholesterol acyltransferase.

To gain insight into metabolic determinants of high density lipoproteins (HDL) containing apolipoproteins A-I and A-II (LpA-I/A-II) and those containing A-I, but devoid of A-II (LpA-I), the plasma concentration of LpA-I and LpA-I/A-II within the HDL2 and HDL3 density spectrum was measured in 14 normolipidemic male subjects on a standardized diet. Apolipoprotein plasma concentrations of HDL subspecies were compared with the magnitude of postprandial lipemia, activities of lipoprotein lipase and hepatic lipase in postheparin plasma, plasma lecithin:cholesterol acyltransferase (LCAT) activity, and cholesteryl ester transfer protein (CETP) mass. Plasma levels of LpA-I/A-II were 2.5 times higher than levels of LpA-I (123 +/- 20 vs. 48.3 +/- 22.1 mg protein/dl) and the partition of LpA-I and LpA-I/A-II between HDL2 and HDL3 differed in that the proportion of LpA-I associated with HDL2 was greater than that of LpA-I/A-II (23 +/- 19 vs. 6 +/- 6%, P < 0.002). With increasing levels of HDL2, the proportion of LpA-I in HDL2 increased (P < 0.002). Furthermore, levels of LpA-I and LpA-I/A-II were strongly correlated within the HDL2 but not within the HDL3 density region. Plasma levels of LpA-I, but not LpA-I/A-II, were inversely correlated with the magnitude of postprandial lipemia. However, activities of lipoprotein lipase and hepatic lipase tended to show stronger associations with the partition of LpA-I/A-II between HDL2 and HDL3 than with that of LpA-I. Within the HDL3, but not the HDL2 density spectrum, LpA-I/A-II exhibited a positive association with plasma LCAT activity, while LpA-I displayed an inverse association with plasma CETP mass. These results are consistent with differences in substrate properties of LpA-I and LpA-I/A-II for lipoprotein modifying enzymes and imply different, but overlapping metabolic pathways of LpA-I and LpA-I/A-II.

Adult↗
PubMed1996

Short-term effects of a high-sucrose diet on plasma lipid, lipoprotein cholesterol, tissue lipoprotein lipase and hepatic triglyceride lipase in rats.

Short-term (2 weeks) effects of a high-sucrose diet on plasma lipids, lipoproteins, tissue lipoprotein lipase (LPL) and hepatic triglyceride lipase (HTGL) activities were investigated in rats. Three days of sucrose feeding significantly increased plasma TG (42 +/- 3 mg/dl vs. 56 +/- 2 mg/dl, p = 0.032), while TC increased significantly after 10 days of the diet (50 +/- 2 mg/dl vs. 62 +/- 2 mg/dl, p = 0.0001). HDL-C increased significantly after 3 days of sucrose feeding (36.2 +/- 0.9 mg/dl vs. 42.4 +/- 2.7 mg/dl, p = 0.011). Although LDL-C tended to decrease on days 3, 7 and 10, these changes were not significant. The plasma glucose level did not change during the study. Increased LPL activity in adipose tissue and decreased enzyme activities in skeletal and heart muscles were observed. Adipose tissue LPL returned to the baseline value after 14 days of the diet treatment, while LPL in skeletal and heart muscles remained at the decreased level. HTGL and HTGL/total liver lipase activities were significantly increased after 14 days of the diet. The different responses of lipase activities in various tissues may help to regulate serum lipid and lipoprotein levels in sucrose-fed rats.

Adipose Tissue↗
PubMed1995

On the interfacial activation of Candida antarctica lipase A and B as compared with Humicola lanuginosa lipase.

The interfacial activation of Candida antarctica lipase A (CALA) and B (CALB) has been investigated and compared with that of Humicola lanuginosa lipase (HLL). CALB displayed no interfacial activation towards p-nitrophenyl butyrate (PNPB) when exceeding the solubility limit of the substrate. No activation was observed towards p-nitrophenyl acetate (PNPA) at the addition of sodium dodecyl sulfate (SDS) nor in the presence of a solid polystyrene surface. The catalytic action of CALB was very different from that of Humicola lanuginosa lipase, which showed a pronounced interfacial activation with the same substrates. The basis for the anomalous behaviour of CALB is proposed to be due to the absence of a lid that regulates the access to the active site. In contrast to CALB, CALA expressed interfacial activation, but the activation was not as prominent as for Humicola lanuginosa lipase (HLL). The structural basis for the activation of CALA is unknown.

Adsorption↗
PubMed1994

Cloning of the classical guinea pig pancreatic lipase and comparison with the lipase related protein 2.

Starting from total pancreatic mRNAs, the classical guinea pig pancreatic lipase was cloned using rapid amplification of 3' and 5' cDNA ends. Internal oligonucleotide primers were designed from a partial cDNA clone including the region coding for the lid domain. Using this strategy, we did not amplify the cDNA corresponding to the pancreatic lipase related protein 2 in which the lid domain is deleted. Amino acid sequences of the classical guinea pig pancreatic lipase and the related protein 2 were compared based on the primary and tertiary structures of the classical human pancreatic lipase. Their distinct physiological roles are discussed in the light of functional amino acid differences.

Amino Acid Sequence↗
PubMed2003

High-level expression of a lipase from Bacillus thermocatenulatus BTL2 in Pichia pastoris and some properties of the recombinant lipase.

The BTL2 lipase gene from Bacillus thermocatenulatus was subcloned into the pPICZalphaA vector and integrated further into the genome of Pichia pastoris GS115. One of the best transformants harboring the linearized plasmid pPalpha-BTL2 integrating into the P. pastoris genomic DNA was cultivated in a 5-L bioreactor filled with 4L of the culture medium BMMY. The BTL2 lipase was produced as an extracellular protein in large quantities of 309,000U/L supernatant. The lipase was purified using butyl-Sepharose with a specific activity of 23,000U/mg protein towards tributyrin. The pure enzyme was characterized and its physicochemical properties were compared to those of the BTL2 lipase, which had previously been expressed in Escherichia coli under the control of its native promoter on pUC18 or under the control of the strong temperature inducible promoter lambdaP(L), yielding 600U/g or 54,000U/g wet cells, respectively. The three proteins showed the same N-terminal sequence and had very similar pH optimum, pH stability, temperature optimum, thermostability, and substrate specificity profiles. Three enzymes were extremely stable in the presence of several organic solvents and detergents.

Bacillus↗
PubMed1976

Mechanism of pancreatic lipase action. 1. Interfacial activation of pancreatic lipase.

Hydrolysis of dissolved p-nitrophenyl acetate by pancreatic lipase follows the classical acyl enzyme pathway already proposed for other esterases. Kinetic parameters of the hydrolysis have been determined. The turnover rate of the reaction is many orders of magnitude slower than that for the natural emulsified substrates. Nevertheless, several arguments are in favor of the specificity of this hydrolysis: (1) triacetin, which resembles the usual substrates for the enzyme, is also hydrolyzed very slowly in solution; (2) dissolved triacetin and tripropionin are competitive inhibitors for the p-nitrophenyl acetate hydrolysis; (3) the same chemical structural features which are required in the case of emulsified substrates are also necessary to promote hydrolysis of dissolved p-nitrophenyl esters. This suggests that the same active site (or part of the same active site) is responsible for hydrolysis of both p-nitrophenyy acetate and specific emulsified substrates. Since deacylation is the rate-limiting step in the catalysis of p-nitrophenyl acetate, the intermediate acetyl enzyme can be isolated by trapping it at pH 5.0. Kinetic competence of this intermediate has been demonstrated. Hydrolysis by pancreatic lipase of dissolved monomeric p-nitrophenyl acetate and triacetin is considerably enhanced (100- to 500-fold) by various interfaces. This suggests that at least the deacylation step, which is rate limiting in absence of interface, is accelerated by the presence of inert interfaces. Siliconized glass beads were directly shown to accelerate the deacylation of isolated [3H]acetyl lipase by at least a hundred times. This step does not directly involve the ester substrate.Thus, it is suggested that a part of the activation of lipase at interfaces may be due to a conformational change resulting from adsorption.

Acetates↗
PubMed2003

Evidence that hepatic lipase and endothelial lipase have different substrate specificities for high-density lipoprotein phospholipids.

Hepatic lipase (HL) and endothelial lipase (EL) are both members of the triglyceride lipase gene family. HL hydrolyzes phospholipids and triglycerides in triglyceride-rich lipoproteins and high-density lipoproteins (HDL). EL hydrolyzes HDL phospholipids and has low triglyceride lipase activity. The aim of this study was to determine if HL and EL hydrolyze different HDL phospholipids and whether HDL phospholipid composition regulates the interaction of EL and HL with the particle surface. Spherical, reconstituted HDL (rHDL) containing either 1-palmitoyl-2-oleoylphosphatidylcholine (POPC), 1-palmitoyl-2-linoleoylphosphatidylcholine (PLPC), 1-palmitoyl-2-arachidonylphosphatidylcholine (PAPC), or 1-palmitoyl-2-docosahexanoylphosphatidylcholine (PDPC) as the only phospholipid, apolipoprotein A-I as the only apolipoprotein, and either cholesteryl esters (CE) only or mixtures of CE and triolein (TO) in their core were prepared. The rHDL were similar in size and had comparable core lipid/apoA-I molar ratios. The CE-containing rHDL were used to determine the kinetics of HL- and EL-mediated phospholipid hydrolysis. For HL the V(max) of phospholipid hydrolysis for (POPC)rHDL > (PLPC)rHDL approximately (PDPC)rHDL > (PAPC)rHDL, while the K(m)(app) for (POPC)rHDL > (PDPC)rHDL > (PLPC)rHDL > (PAPC)rHDL. For EL the V(max) for (PDPC)rHDL > (PAPC)rHDL > (PLPC)rHDL approximately (POPC)rHDL, while the K(m)(app) for (PAPC)rHDL approximately (PLPC)rHDL > (POPC)rHDL > (PDPC)rHDL. The kinetics of EL- and HL-mediated TO hydrolysis was determined using rHDL that contained TO in their core. For HL the V(max) of TO hydrolysis for (PLPC)rHDL > (POPC)rHDL > (PAPC)rHDL > (PDPC)rHDL, while the K(m)(app) for (PLPC)rHDL > (POPC)rHDL approximately (PAPC)rHDL > (PDPC)rHDL. For EL the V(max) and K(m)(app) for (PAPC)rHDL > (PDPC)rHDL > (PLPC)rHDL > (POPC)rHDL. These results establish that EL and HL have different substrate specificities for rHDL phospholipids and that their interactions with the rHDL surface are regulated by phospholipids.

Animals↗
PubMed1978

Changes in the lipoprotein lipase (clearing-factor lipase) activity of white adipose tissue during development of the rat.

The lipoprotein lipase (clearing-factor lipase) activity of the white adipose tissue from rats aged between 1 and 145 days was determined. Five adipose-tissue sites (epididymal, uterine, subcutaneous, perirenal and intramuscular) together with serum concentrations of triacylglycerol, cholesterol and glucose were studied. The pattern of enzyme-activity change was remarkably similar in all the sites studied, although the growth of the tissues proceeded non-uniformly. After a peak of activity early in suckling, lipoprotein lipase activity fell to low values by 20 days of age. At weaning (21 days) the activity increased sharply and within 5 days high values were regained. The serum triacylglycerol and cholesterol concentrations were low at birth and reached peaks of concentration coincidentally with the minima of white-adipose-tissue lipoprotein lipase activities, seen late in suckling. The changes in enzyme activity were related to other metabolic changes in adipose tissue and with the known changes in plasma insulin concentrations occurring during development.

Adipose Tissue↗
PubMed1993

Use of pyrenemethyl laurate for fluorescence-based determination of lipase activity in intact living lymphoblastoid cells and for the diagnosis of acid lipase deficiency.

Pyrenemethyl laurate (PMLes), a fluorogenic substrate for determining in vitro lipase activity [Nègre, Salvayre, Dagan and Gatt (1989) Biochim. Biophys. Acta 1006, 84-88], has been administered to cultured lymphoblastoid cells from normal subjects and from a patient affected with Wolman disease, which is characterized by a deficiency of lysosomal acid lipase. The intracellular degradation of PMLes was dependent on the mode of administration of the substrate into the cells, and occurred by two separate pathways involving lysosomal and extra-lysosomal hydrolases. PMLes incorporated into LDL was taken up by normal lymphoblastoid cells through the apolipoprotein-B/E-receptor-mediated pathway and degraded in the lysosomal compartment, as suggested by the degradation block in Wolman cells. In contrast, when PMLes dissolved in 2% dimethyl sulphoxide was added directly to the culture medium, its hydrolysis was similar in lymphoblastoid cells from controls and from patients affected with Wolman disease, neutral lipid storage disease or familial hypercholesterolaemia. This suggested that the administered PMLes was degraded by a non-lysosomal enzyme which is not deficient in Wolman cells. This enzyme also differs from the neutral lipase system which is deficient in lymphoblastoid cells from patients with neutral lipid storage disease. When pyrenemethanol was administered directly to the cell culture, it was only poorly acylated and was rapidly released into the culture medium. These results and the fluorescence properties of PMLes ('monomeric' emission in a hydrophobic environment and 'excimeric' emission in a hydrophilic environment) and pyrenemethanol ('monomeric' emission in a hydrophilic environment) allowed us to design a 'direct reading' procedure by monitoring (without any lipid extraction) the fluorescence of intact living cells and that of the culture medium during pulse-chase experiments. This method allowed the direct evaluation of the time course of in situ degradation of PMLes. In pulse-chase experiments with LDL-PMLes, the fluorescence of normal cells decreased relatively rapidly with time whereas the fluorescence of the culture medium increased concomitantly. With Wolman cells, the cellular fluorescence decreased only very slightly, whereas that of the culture medium remained at the basal level; this demonstrates the catabolic block in intact living cells from patients with Wolman disease. In vitro degradation of PMLes indicated the existence of two PMLes-degrading enzymes in lymphoblastoid cell homogenates: one is the acid lipase which is involved in PMLes degradation in the lysosomal compartment (and is deficient in Wolman cells), while the second is a cytoplasmic enzyme (not deficient in Wolman cells).

Biological Transport↗
PubMed1976

Lipoprotein lipase and hormone-sensitive lipase activities in human subcutaneous lipomas: comparison with normal subcutaneous adipose tissue.

1. Lipoprotein lipase activity and hormone-sensitive lipase activity were investigated in subcutaneous lipomas removed from two patients and compared with the enzyme activities in subcutaneous adipose tissue from two normal subjects. 2. Confirmation was obtained of the presence of lipoprotein lipase activity in lipomas with an activity fifteen to forty-five times that in the two control samples. 3. Hormone-sensitive lipase activity was demonstrated in lipomas under basal conditions of assay as well as in the presence of adrenaline plus theophylline. However, compared with the non-lipomatous fat samples, these activities were lower, as was the magnitude of the lipolytic response to adrenaline plus theophylline. 4. The significance of these measurements of enzyme activity and their role in the pathogenesis of lipomas are briefly discussed.

Adipose Tissue↗
PubMed2005

A novel lipase belonging to the hormone-sensitive lipase family induced under starvation to utilize stored triacylglycerol in Mycobacterium tuberculosis.

Twenty-four putative lipase/esterase genes of Mycobacterium tuberculosis H37Rv were expressed in Escherichia coli and assayed for long-chain triacylglycerol (TG) hydrolase activity. We show here that the product of Rv3097c (LIPY) hydrolyzed long-chain TG with high specific activity. LIPY was purified after solubilization from inclusion bodies; the enzyme displayed a K(m) of 7.57 mM and V(max) of 653.3 nmol/mg/min for triolein with optimal activity between pH 8.0 and pH 9.0. LIPY was inhibited by active serine-directed reagents and was inactivated at temperatures above 37 degrees C. Detergents above their critical micellar concentrations and divalent cations inhibited the activity of LIPY. The N-terminal half of LIPY showed sequence homology with the proline glutamic acid-polymorphic GC-rich repetitive sequences protein family of M. tuberculosis. The C-terminal half of LIPY possesses amino acid domains homologous with the hormone-sensitive lipase family and the conserved active-site motif GDSAG. LIPY shows low sequence identity with the annotated lipases of M. tuberculosis and with other bacterial lipases. We demonstrate that hypoxic cultures of M. tuberculosis, which had accumulated TG, hydrolyzed the stored TG when subjected to nutrient starvation. Under such conditions, lipY was induced more than all lipases, suggesting a central role for it in the utilization of stored TG. We also show that in the lipY-deficient mutant, TG utilization was drastically decreased under nutrient-deprived condition. Thus, LIPY may be responsible for the utilization of stored TG during dormancy and reactivation of the pathogen.

Amino Acid Sequence↗
PubMed2006

Adipose triglyceride lipase and hormone-sensitive lipase are the major enzymes in adipose tissue triacylglycerol catabolism.

The mobilization of free fatty acids from adipose triacylglycerol (TG) stores requires the activities of triacylglycerol lipases. In this study, we demonstrate that adipose triglyceride lipase (ATGL) and hormone-sensitive lipase (HSL) are the major enzymes contributing to TG breakdown in in vitro assays and in organ cultures of murine white adipose tissue (WAT). To differentiate between ATGL- and HSL-specific activities in cytosolic preparations of WAT and to determine the relative contribution of these TG hydrolases to the lipolytic catabolism of fat, mutant mouse models lacking ATGL or HSL and a mono-specific, small molecule inhibitor for HSL (76-0079) were used. We show that 76-0079 had no effect on TG catabolism in HSL-deficient WAT but, in contrast, essentially abolished free fatty acid mobilization in ATGL-deficient fat. CGI-58, a recently identified coactivator of ATGL, stimulates TG hydrolase activity in wild-type and HSL-deficient WAT but not in ATGL-deficient WAT, suggesting that ATGL is the sole target for CGI-58-mediated activation of adipose lipolysis. Together, ATGL and HSL are responsible for more than 95% of the TG hydrolase activity present in murine WAT. Additional known or unknown lipases appear to play only a quantitatively minor role in fat cell lipolysis.

1-Acylglycerol-3-Phosphate O-Acyltransferase↗