Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.1.34 (lipoprotein lipase)
 7,025 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Yeast cells carrying intronless mono- and diacylglycerol lipase (MDGL) genes, constructed by recombination of the genomic gene and cDNA, secreted MDGL into the culture supernatant. Most of the yeast MDGL were extensively glycosylated while they had a similar glyceride specificity to that of native MDGL. Site-directed mutagenesis was used to directly confirm the involvements in enzyme activity of the presumptive amino acid residues to form the catalytic center of MDGL. These residues were conserved in the primary structure alignment of a lipase family from filamentous fungi. Mutant lipase proteins in which Ser83, Ser145, or His259 was replaced with glycine were secreted by yeast transformants as inactive proteins. Mutant proteins replacing Asp199 with glycine or asparagine were not detected in the culture supernatant. Replacing other two highly conserved aspartic acids (at positions 232 and 243) with glycine did not render the enzyme inactive. These results indicate that Ser83, Ser145, and His259 in MDGL, are essential to enzyme activity. Asp199 is also likely to be involved.
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PMID:Secretion of mono- and diacylglycerol lipase from Penicillium camembertii U-150 by Saccharomyces cerevisiae and site-directed mutagenesis of the putative catalytic sites of the lipase. 136 4

We have previously reported two common lipoprotein lipase (LPL) gene mutations underlying LPL deficiency in the majority of 37 French Canadians (Monsalve et al., 1990. J. Clin. Invest. 86: 728-734; Ma et al., 1991. N. Engl. J. Med. 324: 1761-1766). By examining the 10 coding exons of the LPL gene in another French Canadian patient, we have identified a third missense mutation that is found in two of the three remaining patients for whom mutations are undefined. This is a G to A transition in exon 6 that results in a substitution of asparagine for aspartic acid at residue 250. Using in vitro site-directed mutagenesis, we have confirmed that this mutation causes a catalytically defective LPL protein. In addition, the Asp250----Asn mutation was also found on the same haplotype in an LPL-deficient patient of Dutch ancestry, suggesting a common origin. This mutation alters a TaqI restriction site in exon 6 and will allow for rapid screening in patients with LPL deficiency.
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PMID:A missense mutation (Asp250----Asn) in exon 6 of the human lipoprotein lipase gene causes chylomicronemia in patients of different ancestries. 163 92

We are studying naturally occurring mutations in the gene for lipoprotein lipase (LPL) to advance our knowledge about the structure/function relationships for this enzyme. We and others have previously described 11 mutations in human LPL gene and until now none of these directly involves any of the residues in the proposed Asp156-His241-Ser132 catalytic triad. Here we report two separate probands who are deficient in LPL activity and have three different LPL gene haplotypes, suggesting three distinct mutations. Using polymerase chain reaction cloning and DNA sequencing we have identified that proband 1 is a compound heterozygote for a G----A transition at nucleotide 721, resulting in a substitution of asparagine for aspartic acid at residue 156, and a T----A transversion, resulting in a substitution of serine for cysteine at residues 216. Proband 2 is homozygous for an A----G base change at nucleotide 722, leading to a substitution of glycine for aspartic acid at residue 156. The presence of these mutations in the patients and available family members was confirmed by restriction analysis of polymerase chain reaction-amplified DNA. In vitro site-directed mutagenesis and subsequent expression in COS cells have confirmed that all three mutations result in catalytically defective LPL. The two naturally occurring mutations, which both alter the same aspartic acid residue in the proposed Asp156-His241-Ser132 catalytic triad of human LPL, indicate that Asp156 plays a significant role in LPL catalysis. The Cys216----Ser mutation destroys a conserved disulfide bridge that is apparently critical for maintaining LPL structure and function.
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PMID:Two naturally occurring mutations at the first and second bases of codon aspartic acid 156 in the proposed catalytic triad of human lipoprotein lipase. In vivo evidence that aspartic acid 156 is essential for catalysis. 173 Jul 27

Lipoprotein lipase synthesized by cultured rat preadipocytes is present in three compartments: an intracellular, a surface-related 3-min heparin-releasable, and that secreted into the culture medium. 30 min after addition of 6 microM monensin, the lipoprotein lipase activity in the heparin-releasable compartment starts to decrease; by 4 h of monensin treatment the lipoprotein lipase activity in the heparin-releasable pool and in the culture medium is about 10% of that found in control dishes. The intracellular activity, which had been identified as lipoprotein lipase by an antiserum to lipoprotein lipase, increases slowly and doubles by 24 h. However, since the cellular compartment accounts for 10-25% of total activity, this increase does not account for the missing enzyme activity. To determine whether this enzyme molecule is synthesized but is not active, incorporation of labeled leucine, mannose and galactose into immunoadsorbable lipoprotein lipase was studied in control, monensin- or tunicamycin-treated cells. Addition of tunicamycin (5 micrograms/ml) for 24 h caused a 30-50% reduction in immunoadsorbable lipoprotein lipase, but the enzyme activity was reduced by 90%. On the other hand, 4 h monensin treatment reduced both incorporation of [3H]leucine into immunoadsorbable lipoprotein lipase and heparin-releasable and medium lipoprotein lipase activity by 57 to 77%. The immunoadsorbable lipoprotein lipase in the intracellular compartment has a [14C]mannose to [3H]galactose ratio of 0.15 and this ratio increased 6-fold in monensin-treated cells. The intracellular lipoprotein lipase in monensin-treated cells had the same affinity for both the native and synthetic substrate as the lipoprotein lipase in control cells, yet its spontaneous secretion into the culture medium and its release by 3 min heparin treatment was markedly decreased. The present results indicate that: the presence of asparagine-linked oligosaccharide (formation of which is inhibited by tunicamycin) is mandatory for the expression of lipoprotein lipase activity; lipoprotein lipase is active also in a high mannose form; and terminal glycosylation and oligosaccharide processing, which is inhibited by monensin, may be important for the appearance of heparin-releasable lipoprotein lipase and secretion of lipoprotein lipase into the medium.
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PMID:Importance of the different steps of glycosylation for the activity and secretion of lipoprotein lipase in rat preadipocytes studied with monensin and tunicamycin. 405 41

A mutation in the lipoprotein lipase (LPL) gene, resulting in the substitution of asparagine by serine at residue 291 (LPL-S291), was found to occur in young survivors of a myocardial infarction from Sweden, combined hyperlipidemic subjects from the United Kingdom, and type III hyperlipidemic subjects from Germany at allelic carrier frequencies no different from those found in companion healthy control subjects (3.63 vs. 3.37; 1.85 vs. 1.60; and 2.00 vs. 1.56%, respectively). In a group of 620 healthy middle-aged men from the United Kingdom with baseline and three subsequent annual lipid measurements, mean plasma triacylglycerol (TG), (but not plasma cholesterol) concentrations in carriers of the mutation were significantly elevated over non-carriers (1.95 vs. 1.61 mmol/l, P = 0.05, and 5.83 vs. 5.65 mmol/l, P = 0.29, respectively). When these healthy control subjects were divided according to tertiles of body mass index (BMI), as expected, non-carriers whose BMI was in the upper two tertiles (BMI > or = 25.0 kg/m2) had higher plasma TG concentrations than those in the lowest tertile (1.90 vs. 1.54 mmol/l), but this difference was much greater in LPL-S291 carriers (2.33 vs. 1.36 mmol/l, P = 0.01, BMI x genotype interaction, P = 0.02). To confirm this effect, a second group of 319 healthy subjects from the United Kingdom was screened for LPL-S291. The allelic frequency of the mutation was found to be 1.88% and the effect on plasma lipid concentrations was very similar to that observed in the first control group (plasma TG, 2.31 vs. 1.27 mmol/l, P < 0.001 for LPL-S291 carriers vs. non-carriers, respectively). As before, those carriers whose BMI was in the top two tertiles for this sample (BMI > or = 23.3 kg/m2) had higher plasma TG concentrations than non-carriers (2.31 vs. 1.42 mmol/l). Thus, the LPL-S291 variant may predispose individuals to elevated plasma TG concentrations under conditions such as increased BMI.
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PMID:Interaction of the lipoprotein lipase asparagine 291-->serine mutation with body mass index determines elevated plasma triacylglycerol concentrations: a study in hyperlipidemic subjects, myocardial infarction survivors, and healthy adults. 857 37

Using polymerase chain reaction (PCR) based techniques, we have identified individuals in the ECTIM study of myocardial infarction survivors (cases) and healthy matched controls who are carriers for a mutation of the gene for lipoprotein lipase (LPL) which alters amino acid 9 from aspartic acid to asparagine (LPL-D9N). The frequency of carriers in the cases from Belfast and France (3 separate centres) was 2.5 and 3.7%, respectively (mean 3.3%, 95% CI 1.9-4.7) and in the controls 2.0 and 2.9%, respectively (mean 2.7%, 95% CI 1.6-3.8%), but this difference was not statistically significant. In the cases, carriers of the allele for LPL-N9 had higher levels of several plasma lipid traits including total triglycerides (TG) (30%), very low density lipoprotein (VLDL) cholesterol (19%), apo E (24%), apo C-III (17%), lipoprotein particles (Lp) containing both apo E and apo B (LpE:B) (32%), and particles containing both apo C-III and apo B (LpCIII:B) (39%), and this effect was consistent in cases both from Belfast and from the French centres combined. By contrast, in the controls there were no differences in any lipid trait between carriers and non-carriers of the mutation that was consistent between the French centres and Belfast. There were no significant differences in the levels of any measured factor between cases and controls that could explain the different effect on plasma lipid traits associated with the mutation. However, compared to the non-carriers, in both cases and controls who carried the mutation, plasma TG concentrations were higher in those whose body mass index (BMI) was above the mean of the sample (26.0 kg/m2), with statistically significant interaction seen between BMI and genotype and levels of apo C-III, and lipoprotein particles containing both apo C-III and apo B (P < 0.02). The data suggest that carriers for the LPL-N9 mutation have a mild genetic predisposition to developing hyperlipidaemia and an atherogenic lipid profile, but that this requires the presence of other genetic or environmental factors for full expression, one of which appears to be increasing obesity.
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PMID:Association between the LPL-D9N mutation in the lipoprotein lipase gene and plasma lipid traits in myocardial infarction survivors from the ECTIM Study. 872 8

Familial lipoprotein lipase (LPL) deficiency is an inherited disorder of lipoprotein metabolism characterized by hypertriglyceridemia and recurrent episodes of abdominal pain and pancreatitis. We have studied the genetic basis of LPL deficiency in a 62-year-old black male with undetectable pre- and post-heparin plasma LPL mass and activity, DNA sequence analysis of the patient's LPL cDNA and gene as well as digestion with Bcl I and Asu I revealed that the proband is a homozygote for two separate gene defects. One mutation changed a G to an A, resulting in the conversion of amino acid 9 of the mature protein, aspartic acid (GAC), to asparagine (AAC). The second substitution, a C for a T, replaced tyrosine (TAC) at residue 262 with histidine (CAC). Northern blot analysis of monocyte-derived macrophage RNA demonstrated the presence of LPL mRNA of approximately normal size and quantity when compared to control. Expression of both mutations separately (pCMV-9 and pCMV-262) or in combination (pCMV-9+262) in human embryonal kidney-293 cells demonstrated that LPL-9 had approximately 80% the specific activity of wild type LPL, but LPL-262 and LPL-9+262 had no enzymic activity, thus establishing the functional significance of the LPL-262 defect. Despite an absolute deficiency of LPL mass and activity demonstrated by analysis of patient post-heparin plasma, in vitro expression of both LPL mutants was normal, suggesting that the absence of LPL in patient post-heparin plasma was a result of altered in vivo processing. Analysis of the heparin binding properties of the mutant enzymes by heparin-Sepharose affinity chromatography indicated that most of the LPL-262 mass was present in an inactive peak, which like the normal LPL monomer, eluted at 0.8 M NaCl. Thus, the Tyr262 --> His mutation may alter the stability of the LPL dimer, leading to the formation of inactive LPL-262 monomer which exhibits reduced heparin affinity. Based on these results, we propose that, in vivo, enhanced formation of LPL-9+262 monomer leads to abnormal binding of the mutant lipase to endothelial glycosaminoglycans ultimately resulting in enhanced catabolism of the mutant enzyme and lower enzyme mass in post-heparin plasma.
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PMID:Homozygosity for two point mutations in the lipoprotein lipase (LPL) gene in a patient with familial LPL deficiency: LPL(Asp9-->Asn, Tyr262-->His). 872 26

The interaction of lipoprotein lipase (LPL) with heparan sulfate proteoglycans plays an important role in the metabolism and catalytic function of the enzyme. We have used site-directed mutagenesis to replace the basic residues contained in a discontinuous charge cluster (residues Lys 321, Arg 405, Arg 407, Lys 409, Lys 415, and Lys 416) of avian LPL with asparagine. The mutant proteins were expressed in Chinese hamster ovary cells and their affinity for heparin was evaluated by heparin-Sepharose chromatography. Mutation of residues Lys 321, Arg 405, Arg 407, Lys 409, and Lys 416 resulted in a decrease in affinity for heparin. The triple mutant LPL(R405N, R407N, K409N) possessed almost no high-affinity binding. The LPL mutants showed enzymatic activities ranging between 50-100% of that seen for wild-type LPL demonstrating that the overall structure of the enzyme was not significantly altered by the mutations. Mutation of previously identified heparin-binding regions of LPL results in a relatively small decrease in heparin-binding affinity, as compared with mutations in this carboxyl-terminal region, indicating that Lys 321, Arg 405, Arg 407, Lys 409, and Lys 416 constitute the major heparin-binding domain in LPL.
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PMID:Identification of a heparin-binding domain in the distal carboxyl-terminal region of lipoprotein lipase by site-directed mutagenesis. 964 64

Genetic variants of lipoprotein lipase (LPL), a key enzyme in the hydrolysis of triglyceride (TG)-rich particles, may contribute to ischaemic heart disease (IHD) risk. We have examined the risk of IHD in carriers of two common LPL variants, asparagine substitution for aspartic acid at residue 9 (D9N) and serine for asparagine at residue 291 (N291S) in 2708 middle-aged healthy European men, followed for over 6 years. The carrier frequencies were 2.6% for N9, and 3.9% for S291. Both variants were associated with higher plasma TG at baseline of 9% and 14%, respectively. At baseline, 28% of men were current smokers and smoking was unrelated to genotype. Associations between LPL variants and disease outcome, according to smoking status, were assessed by Cox's proportional hazards analysis. S291 carriers showed no increased risk of IHD compared to non-carriers, while there was strong evidence of interaction between D9N genotype and smoking status (P = 0.0003) in determining the risk of IHD. In 2248 non-carriers of N9, smoking increased the risk of an IHD event by 1.6 (95% CI: 1.1-2.4%) times. Among 58 N9 carriers, no IHD events occurred in 42 who were non-smokers, whereas five events were reported in 16 who smoked. The combined effect of smoking and N9 allele was to increase the risk of an IHD event by 10.4 (95% CI: 4.7-22.8%) times compared with D9 non-smokers. These findings could not be explained by confounding effects of baseline TG. Carriers of N9 appear to be especially vulnerable to the adverse effects of cigarette smoking on IHD risk, but this susceptibility is unrelated to the influence of this variant on plasma TG levels.
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PMID:Substitution of asparagine for aspartic acid at residue 9 (D9N) of lipoprotein lipase markedly augments risk of ischaemic heart disease in male smokers. 1070 17

Two novel mutations in the lipoprotein lipase (LPL) gene are described in an Austrian family: a splice site mutation in intron 1 (3 bp deletion of nucleotides -2 to -4) which results in skipping of exon 2, and a missense mutation in exon 5 which causes an asparagine for histidine substitution in codon 183 and complete loss of enzyme activity. A 5-year-old boy who exhibited all the clinical features of primary hyperchylomicronemia was a compound heterozygote for these two mutations. Nine other family members were investigated: seven were heterozygotes for the splice site mutation, one was a heterozygote for the missense mutation, and one had two wild-type alleles of the LPL gene. LPL activity in the post-heparin plasma of the heterozygotes was reduced to 49;-79% of the mean observed in normal individuals. Two of the heterozygotes had extremely high plasma triglyceride levels; in three of the other heterozygotes the plasma triglycerides were also elevated. As plasma triglycerides in carriers of one defective LPL allele can be normal or elevated, the heterozygotes of this family have been studied for a possible additional cause of the expression of hypertriglyceridemia in these subjects. Body mass index, insulin resistance, mutations in other candidate genes (Asn291Ser and Asp9Asn in the LPL gene, apoE isoforms, polymorphisms in the apoA-II gene and in the apoAI-CIII-AIV gene cluster, and in the IRS-1 gene) could be ruled out as possible factors contributing to the expression of hypertriglyceridemia in this family. A linkage analysis using the allelic marker D1S104 on chromosome 1q21;-q23 suggested that a gene in this region could play a role in the expression of hypertriglyceridemia in the heterozygous carriers of this family, but the evidence was not sufficiently strong to prove this assumption. Nevertheless, this polymorphic marker seems to be a good candidate for further studies.
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PMID:Two novel mutations in the lipoprotein lipase gene in a family with marked hypertriglyceridemia in heterozygous carriers. Potential interaction with the polymorphic marker D1S104 on chromosome 1q21-q23. 1078 34


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