Study of the lecithin:Cholesterol acyltransferase reaction with liposome and high density lipoprotein substrates

Mehrnoosh Jahani, Andras G. Lacko

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12 Citations (Scopus)

Abstract

The activity of highly purified preparations of human plasma lecithin:cholesterol acyltransferase were stabilized by precipitating the enzyme with ammonium sulfate and using the dilutions of the particulate lecithin:cholesterol acyltransferase suspension for enzyme assays. Ammonium sulfate concentrations in the assay mix up to 0.1 M had no significant effect on lecithin:cholesterol acyltransferase activity. The basic enzymatic properties of lecithin : cholesterol acyltransferase were investigated using liposomes and high density lipoprotein (HDL) substrates. pH optima for both substrates was approximately 8.0. The temperature dependence of lecithin : cholesterol acyltransferase activity resulted in non-linear Arrhenius plots with both substrates. The activity vs. temperature (°C) curves showed slight inflections at 30°C, which may have been due to the relatively rapid inactivation of the enzyme above this temperature. HDL3 was found to be a better substrate than HDL or HDL2. HDL3 was also considerably better than egg phosphatidylcholine/cholesterol liposomes as an lecithin:cholesterol acyltransferase substrate. Addition of HDL2 to a reaction mix of enzyme and HDL, indicated that HDL2 acts as an inhibitor of cholesterol esterification in this system.

Original languageEnglish
Pages (from-to)504-511
Number of pages8
JournalBiochimica et Biophysica Acta (BBA)/Lipids and Lipid Metabolism
Volume713
Issue number3
DOIs
StatePublished - 13 Dec 1982

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Phosphatidylcholine-Sterol O-Acyltransferase
HDL Lipoproteins
Liposomes
Substrates
HDL2 Lipoprotein
Ammonium Sulfate
Enzymes
Temperature
Assays
Thermodynamic properties
Anticholesteremic Agents
Plasma (human)
Arrhenius plots
Esterification
Enzyme Assays
Phosphatidylcholines
Dilution
Ovum
Suspensions
Cholesterol

Keywords

  • HDL
  • Lecithin
  • Lipoprotein
  • Liposome
  • cholesterol acyltransferase

Cite this

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abstract = "The activity of highly purified preparations of human plasma lecithin:cholesterol acyltransferase were stabilized by precipitating the enzyme with ammonium sulfate and using the dilutions of the particulate lecithin:cholesterol acyltransferase suspension for enzyme assays. Ammonium sulfate concentrations in the assay mix up to 0.1 M had no significant effect on lecithin:cholesterol acyltransferase activity. The basic enzymatic properties of lecithin : cholesterol acyltransferase were investigated using liposomes and high density lipoprotein (HDL) substrates. pH optima for both substrates was approximately 8.0. The temperature dependence of lecithin : cholesterol acyltransferase activity resulted in non-linear Arrhenius plots with both substrates. The activity vs. temperature (°C) curves showed slight inflections at 30°C, which may have been due to the relatively rapid inactivation of the enzyme above this temperature. HDL3 was found to be a better substrate than HDL or HDL2. HDL3 was also considerably better than egg phosphatidylcholine/cholesterol liposomes as an lecithin:cholesterol acyltransferase substrate. Addition of HDL2 to a reaction mix of enzyme and HDL, indicated that HDL2 acts as an inhibitor of cholesterol esterification in this system.",
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T1 - Study of the lecithin:Cholesterol acyltransferase reaction with liposome and high density lipoprotein substrates

AU - Jahani, Mehrnoosh

AU - Lacko, Andras G.

PY - 1982/12/13

Y1 - 1982/12/13

N2 - The activity of highly purified preparations of human plasma lecithin:cholesterol acyltransferase were stabilized by precipitating the enzyme with ammonium sulfate and using the dilutions of the particulate lecithin:cholesterol acyltransferase suspension for enzyme assays. Ammonium sulfate concentrations in the assay mix up to 0.1 M had no significant effect on lecithin:cholesterol acyltransferase activity. The basic enzymatic properties of lecithin : cholesterol acyltransferase were investigated using liposomes and high density lipoprotein (HDL) substrates. pH optima for both substrates was approximately 8.0. The temperature dependence of lecithin : cholesterol acyltransferase activity resulted in non-linear Arrhenius plots with both substrates. The activity vs. temperature (°C) curves showed slight inflections at 30°C, which may have been due to the relatively rapid inactivation of the enzyme above this temperature. HDL3 was found to be a better substrate than HDL or HDL2. HDL3 was also considerably better than egg phosphatidylcholine/cholesterol liposomes as an lecithin:cholesterol acyltransferase substrate. Addition of HDL2 to a reaction mix of enzyme and HDL, indicated that HDL2 acts as an inhibitor of cholesterol esterification in this system.

AB - The activity of highly purified preparations of human plasma lecithin:cholesterol acyltransferase were stabilized by precipitating the enzyme with ammonium sulfate and using the dilutions of the particulate lecithin:cholesterol acyltransferase suspension for enzyme assays. Ammonium sulfate concentrations in the assay mix up to 0.1 M had no significant effect on lecithin:cholesterol acyltransferase activity. The basic enzymatic properties of lecithin : cholesterol acyltransferase were investigated using liposomes and high density lipoprotein (HDL) substrates. pH optima for both substrates was approximately 8.0. The temperature dependence of lecithin : cholesterol acyltransferase activity resulted in non-linear Arrhenius plots with both substrates. The activity vs. temperature (°C) curves showed slight inflections at 30°C, which may have been due to the relatively rapid inactivation of the enzyme above this temperature. HDL3 was found to be a better substrate than HDL or HDL2. HDL3 was also considerably better than egg phosphatidylcholine/cholesterol liposomes as an lecithin:cholesterol acyltransferase substrate. Addition of HDL2 to a reaction mix of enzyme and HDL, indicated that HDL2 acts as an inhibitor of cholesterol esterification in this system.

KW - HDL

KW - Lecithin

KW - Lipoprotein

KW - Liposome

KW - cholesterol acyltransferase

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DO - 10.1016/0005-2760(82)90310-1

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