Publications

• Human hepatic and lipoprotein lipase: the loop covering the catalytic site mediates lipase substrate specificity.

  Dugi K.A., Dichek H.L., Santamarina-Fojo S.

  Hepatic lipase (HL) and lipoprotein lipase (LPL) are key enzymes that mediate the hydrolysis of triglycerides (TG) and phospholipids (PL) present in circulating plasma lipoproteins. Relative to triacylglycerol hydrolysis, HL displays higher phospholipase activity than LPL. The structural basis for ... >> More

  Hepatic lipase (HL) and lipoprotein lipase (LPL) are key enzymes that mediate the hydrolysis of triglycerides (TG) and phospholipids (PL) present in circulating plasma lipoproteins. Relative to triacylglycerol hydrolysis, HL displays higher phospholipase activity than LPL. The structural basis for this difference in substrate specificity has not been definitively established. We recently demonstrated that the 22-amino acid loops ("lids") covering the catalytic sites of LPL and HL are critical for the interaction with lipid substrate (Dugi, K.A., Dichek, H.L., Talley, G.D., Brewer, H.B., Jr., and Santamarina-Fojo, S. (1992) J. Biol. Chem. 267, 25086-25091). To determine whether the lipase lid plays a role in conferring the different substrate specificities of HL and LPL, we have generated four chimeric lipases. Characterization of these chimeric enzymes using TG (triolein and tributyrin) or PL (dioleoylphosphatidylcholine (DOPC) vesicles, DOPC proteoliposomes, and DOPC-mixed liposomes) substrates demonstrated marked differences between their relative PL/TG hydrolyzing activities. Chimeric LPL containing the lid of HL had reduced triolein hydrolyzing activity (49% of the wild type), but increased phospholipase activity in DOPC vesicle, DOPC proteoliposome, and DOPC-mixed liposome assay systems (443, 628, and 327% of wild-type LPL, respectively). In contrast, chimeric HL containing the LPL lid was more active against triolein (123% of the wild type) and less active against DOPC (23, 0, and 30%, respectively) than normal HL. Similar results were obtained when the lipase lids were exchanged in chimeric enzymes containing the NH2-terminal end of LPL and the COOH-terminal domain of HL. Exchange of the LPL and HL lids resulted in a reversal of the phospholipase/neutral lipase ratio, establishing the important role of this region in mediating substrate specificity. In summary, the lid covering the catalytic domains in LPL and HL plays a crucial role in determining lipase substrate specificity. The lid of LPL confers preferential triglyceride hydrolysis, whereas the lid of HL augments phospholipase activity. This study provides new insight into the structural basis for the observed in vivo differences in LPL and HL function. << Less

  J. Biol. Chem. 270:25396-25401(1995) [PubMed] [EuropePMC]

  This publication is cited by 4 other entries.

• The acylation of lipophilic alcohols by lysosomal phospholipase A2.

  Abe A., Hiraoka M., Shayman J.A.

  A novel lysosomal phospholipase A(2) (LPLA2) with specificity toward phosphatidylethanolamine and phosphatidylcholine was previously purified and cloned. LPLA2 transfers sn-1 or sn-2 acyl groups of phospholipids to the C1 hydroxyl of the short-chain ceramide N-acetylsphingosine (NAS) under acidic ... >> More

  A novel lysosomal phospholipase A(2) (LPLA2) with specificity toward phosphatidylethanolamine and phosphatidylcholine was previously purified and cloned. LPLA2 transfers sn-1 or sn-2 acyl groups of phospholipids to the C1 hydroxyl of the short-chain ceramide N-acetylsphingosine (NAS) under acidic conditions. The common features of lipophilic alcohols serving as acceptor molecules in the transacylase reaction were examined. 1-O-Hexadecyl-2-acetyl-sn-glycerol (HAG) was acylated by LPLA2 similar to NAS. HAG competed with NAS and inhibited NAS acylation. The transacylation of 1-O-hexadecyl-glycerol (HG), 1-O-palmityl-2-O-methyl-sn-glycerol (PMG), and monoacylglycerols was also investigated. HG, PMG, 1- or 3-palmitoyl-sn-glycerol, and 2-palmitoylglycerol were converted to 1,3-alkylacylglycerol, 1,2-dialkyl-3-acylglycerol, 1,3-diacylglycerol, and 1,2- or 2,3-diacylglycerol, respectively. HG and monoacylglycerol inhibited the acylation of NAS by the enzyme with IC(50) values of 35 and 45 microM, respectively. Additionally, the enzyme acylated glycerol to produce 1- or 3-acyl-sn-glycerol but not 2-acylglycerol. Therefore, the preferred acceptor molecules for LPLA2 are primary alcohols with one long carbon chain and one small nonpolar residue linked to the C2 position of ethanol. The enzyme acylated other natural lipophilic alcohols, including anandamide and oleoylethanolamide. Thus, LPLA2 may function to remodel acyl groups and modulate the biological and pharmacological activities of some lipophilic alcohols. << Less

  J. Lipid Res. 48:2255-2263(2007) [PubMed] [EuropePMC]

  This publication is cited by 38 other entries.

• Further biochemical characterization of human pancreatic lipase-related protein 2 expressed in yeast cells.

  Eydoux C., De Caro J., Ferrato F., Boullanger P., Lafont D., Laugier R., Carriere F., De Caro A.

  Recombinant human pancreatic lipase-related protein 2 (rHPLRP2) was produced in the protease A-deficient yeast Pichia pastoris. A major protein with a molecular mass of 50 kDa was purified from the culture medium using SP-Sepharose and Mono Q chromatography. The protein was found to be highly sens ... >> More

  Recombinant human pancreatic lipase-related protein 2 (rHPLRP2) was produced in the protease A-deficient yeast Pichia pastoris. A major protein with a molecular mass of 50 kDa was purified from the culture medium using SP-Sepharose and Mono Q chromatography. The protein was found to be highly sensitive to the proteolytic cleavage of a peptide bond in the lid domain. The proteolytic cleavage process occurring in the lid affected both the lipase and phospholipase activities of rHPLRP2. The substrate specificity of the nonproteolyzed rHPLRP2 was investigated using pH-stat and monomolecular film techniques and various substrates (glycerides, phospholipids, and galactolipids). All of the enzyme activities were maximum at alkaline pH values and decreased in the pH 5-7 range corresponding to the physiological conditions occurring in the duodenum. rHPLRP2 was found to act preferentially on substrates forming small aggregates in solution (monoglycerides, egg phosphatidylcholine, and galactolipids) rather than on emulsified substrates such as triolein and diolein. The activity of rHPLRP2 on monogalactosyldiglyceride and digalactosyldiglyceride monomolecular films was determined and compared with that of guinea pig pancreatic lipase-related protein 2, which shows a large deletion in the lid domain. The presence of a full-length lid domain in rHPLRP2 makes it possible for enzyme activity to occur at higher surface pressures. The finding that the inhibition of nonproteolyzed rHPLRP2 by tetrahydrolipstatin and diethyl-p-nitrophenyl phosphate does not involve any bile salt requirements suggests that the rHPLRP2 lid adopts an open conformation in aqueous media. << Less

  J. Lipid Res. 48:1539-1549(2007) [PubMed] [EuropePMC]

  This publication is cited by 8 other entries.

• Intracellular phospholipase A1 and acyltransferase, which are involved in Caenorhabditis elegans stem cell divisions, determine the sn-1 fatty acyl chain of phosphatidylinositol.

  Imae R., Inoue T., Kimura M., Kanamori T., Tomioka N.H., Kage-Nakadai E., Mitani S., Arai H.

  Phosphatidylinositol (PI), an important constituent of membranes, contains stearic acid as the major fatty acid at the sn-1 position. This fatty acid is thought to be incorporated into PI through fatty acid remodeling by sequential deacylation and reacylation. However, the genes responsible for th ... >> More

  Phosphatidylinositol (PI), an important constituent of membranes, contains stearic acid as the major fatty acid at the sn-1 position. This fatty acid is thought to be incorporated into PI through fatty acid remodeling by sequential deacylation and reacylation. However, the genes responsible for the reaction are unknown, and consequently, the physiological significance of the sn-1 fatty acid remains to be elucidated. Here, we identified acl-8, -9, and -10, which are closely related to each other, and ipla-1 as strong candidates for genes involved in fatty acid remodeling at the sn-1 position of PI. In both ipla-1 mutants and acl-8 acl-9 acl-10 triple mutants of Caenorhabditis elegans, the stearic acid content of PI is reduced, and asymmetric division of stem cell-like epithelial cells is defective. The defects in asymmetric division of these mutants are suppressed by a mutation of the same genes involved in intracellular retrograde transport, suggesting that ipla-1 and acl genes act in the same pathway. IPLA-1 and ACL-10 have phospholipase A(1) and acyltransferase activity, respectively, both of which recognize the sn-1 position of PI as their substrate. We propose that the sn-1 fatty acid of PI is determined by ipla-1 and acl-8, -9, -10 and crucial for asymmetric divisions. << Less

  Mol. Biol. Cell 21:3114-3124(2010) [PubMed] [EuropePMC]

  This publication is cited by 7 other entries.