Purification and properties of human placental acid lipase

Burton, Barbara K.; Mueller, Howard W.

doi:10.1016/0005-2760(80)90263-5

Cited by 31 publications

(13 citation statements)

References 11 publications

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“…The residues involved in the catalytic activity of LAL are not well defined. LAL can be inactivated by chemical modification of both serine and cysteine residues, and thiols are necessary for the stability of the purified enzyme [17][18][19][20]. Gastric lipase has been shown to be a thiol enzyme on the basis of chemical modification by thiol-reactive agents [21,22].…”

Section: Introductionmentioning

confidence: 99%

Cysteine residues in human lysosomal acid lipase are involved in selective cholesteryl esterase activity

Pagani

Pariyarath

Stuani

et al. 1997

Biochemical Journal

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Human lysosomal acid lipase (LAL) catalyses the deacylation of triacylglycerol and cholesteryl esters in the acidic lysosomal compartment. Treatment of LAL with the reducing agent dithiothreitol affected the triacylglycerol and cholesteryl esterase activities differentially, suggesting the involvement of cysteine residues in determining substrate specificity. To identify the residues involved, human LAL cDNA, under the control of the T7 promoter and tagged with a herpes simplex virus coding epitope, was specifically mutated in order to introduce single amino acid substitutions of each of the six cysteine residues of mature LAL. All Cys-227 mutants showed selectively decreased activity towards cholesteryl oleate, while preserving that towards trioleylglycerol. Substitutions of Cys-236, Cys-240 and Cys-244 affected catalysis towards the two substrates to a variable degree, depending on the side chain of the amino acid introduced. The replacement of Cys-41 or Cys-188 did not result in the preferential cleavage of either one of the two substrates. These data indicate that Cys-227, Cys-236, Cys-240 and Cys-244 play a crucial role in determining LAL substrate specificity. We propose that these cysteine residues are involved in the hydrolysis of cholesteryl ester by affecting selectively the access of this substrate to the catalytic active site. In addition, the fact that the catalytic activity is never completely abolished in cysteine mutants demonstrates that LAL is not a thiol enzyme.

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Section: Introductionmentioning

confidence: 99%

Cysteine residues in human lysosomal acid lipase are involved in selective cholesteryl esterase activity

Pagani

Pariyarath

Stuani

et al. 1997

Biochemical Journal

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“…Lipase activities were measured at pH 4 and properties of lipoprotein lipase (6,7), whereas a second, measured pH 8 in the placentas of rats made diabetic by streptozo-at pH 4, is probably lysosomal in origin (8). tocin treatment and also in the placentas of women classiLipoprotein lipase activity in adipose tissue and diaphragm fied as having 1) impaired glucose tolerance or type 2 was found to be reduced in streptozotocin-induced diabetic rats, diabetes, 2) type 1 diabetes with no associated vascular but in the same experiments the lipoprotein lipase-like activity complication, and 3) type 1 diabetes with associated vas-in the placenta was unaffected (9, 10).…”

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confidence: 99%

The Effects of Diabetes on Placental Lipase Activity in the Rat and Human

et al. 1991

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ABSTRACT. Lipase activities were measured at pH 4 and properties of lipoprotein lipase (6,7), whereas a second, measured pH 8 in the placentas of rats made diabetic by streptozo-at pH 4, is probably lysosomal in origin (8). tocin treatment and also in the placentas of women classiLipoprotein lipase activity in adipose tissue and diaphragm fied as having 1) impaired glucose tolerance or type 2 was found to be reduced in streptozotocin-induced diabetic rats, diabetes, 2) type 1 diabetes with no associated vascular but in the same experiments the lipoprotein lipase-like activity complication, and 3) type 1 diabetes with associated vas-in the placenta was unaffected (9, 10). However, Shafrir and cular disease. In both sets of experiments, the placentas coworkers (4, 9) showed that lipolytic activity in the placentas of were compared with normal control groups. The placental diabetic rats was increased, and they inferred that this was due lipase activity measured at pH 8 was not significantly to an increase in placental "intracellular" lipase activity. Theredifferent in either streptozotocin-treated rats or impaired fore, in the study reported here, we tested the hypothesis that glucose toleranceldiabetic women as compared with con-placental pH 4 lipase activity is increased in the placentas of trols, whereas the lipase activity measured at pH 4 in-diabetic women and rats. We have measured both the pH 8 creased significantly as compared with controls in both lipase and the pH 4 lipase activity in the placentas of streptozospecies. Furthermore, in the women there was a significant tocin-induced diabetic rats and also in the placentas of mothers correlation between placental lipase activity at pH 4 and who were classified as having IGT or type 2 diabetes and those birth weight in impaired glucose tolerance/type 2 diabetes. classified as having type 1 diabetes with or without vascular It is suggested that the increased placental lipase activity disease. may contribute to the increased fetal weight in human diabetic pregnancy, by contributing to the increased fat Chemicals and isotopes. 3H-9-10 trioleyl glycerol (sp act 0.5-1.0 Ci/mmol) was purchased from Amersham International plc Abbreviations (Bucks, UK). Phosphatidylcholine, 9-10 trioleyl glycerol (99%) glycerol, and BSA were all purchased from Sigma Chemical IGT, impaired glucose tolerance Company (Dorset, UK). Heat-inactivated horse serum was purchased from Flow Laboratories (Herts, UK). Streptozotocin was kindly provided by Dr. N. MacLeod (The UpJohn Co., Kalamazoo, MI). Other chemicals were ANALAR grade, purchased Diabetes in pregnancy produces major changes in maternal from BDH (Poole, UK). plasma lipid concentrations (1-3). Plasma triglycerides are ele- Streptozotocin-induced diabetes in rats.Female CSE Wistar vated in both type 2 diabetes and gestational diabetes, whereas rats were made diabetic before mating by a single i.v. adminisin type 1 diabetic patients plasma triglycerides are not signifi-tration of 40 mg/kg of streptozotocin (1 1). Serum glucose was c...

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“…Lipid may be transferred from the mother to the fetus across the placenta in the form of free fatty acids (FFA), derived either directly from maternal albumin-bound FFA [1] or from maternal very low density lipoprotein (VLDL) hydrolysed by placental lipases, with the release of fatty acids [2], The pla centa contains a lipoprotein lipase-like en zyme, which hydrolyses the maternal VLDL [3] and also intracellular lipases which hy drolyse stored placental triglyceride [4,5]. To investigate the importance of these en zymes in providing FFA for the developing fetus we modified the lipase assay of Nilsson-Ehle and Schotz [6] to enable us to assay simultaneously placental lipase activities at pH 4 (the optimal pH for one of the intracel lular lipases [4,5]) and at pH 8 (the optimal pH for the lipoprotein lipase-like enzyme [3]).…”

Section: Introductionmentioning

confidence: 99%

Effects of Maternal Undernutrition and Uterine Artery Ligation on Placental Lipase Activities in the Rat

Kaminsky¹,

D'Souza²,

Massey³

et al. 1991

Neonatology

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Lipase activities measured at pH 4 and 8 were determined in the placentas of rats subjected to undernutrition or uterine artery ligation. The fetal lipid content following maternal undernutrition was also determined. The placental lipase activity (per gram placenta) measured at pH 8 (placental lipoprotein lipase) remained unchanged, whilst the activity of the intracellular lipase (per gram placenta) measured at pH 4 was significantly less than in the control group (21 % lower in maternal undernutrition and 16 % lower after uterine artery ligation). Although placentas and fetuses were significantly lighter in both situations as compared to controls (well-nourished or sham operated, respectively), fetal lipid content in maternal undernutrition was only reduced to a degree concomitant with the decrease in fetal weight. We therefore conclude that the intracellular lipase may not have an important role in the provision of free fatty acids in undernutrition.

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Purification and properties of human placental acid lipase

Cited by 31 publications

References 11 publications

Cysteine residues in human lysosomal acid lipase are involved in selective cholesteryl esterase activity

Cysteine residues in human lysosomal acid lipase are involved in selective cholesteryl esterase activity

The Effects of Diabetes on Placental Lipase Activity in the Rat and Human

Effects of Maternal Undernutrition and Uterine Artery Ligation on Placental Lipase Activities in the Rat

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