Human plasma phospholipid transfer protein accelerates exchange/transfer of alpha-tocopherol between lipoproteins and cells.
alpha-Tocopherol (alpha-T), an important anti-oxidant of plasma lipoproteins and cell membranes, is secreted from liver together with very-low-density lipoproteins into the blood stream. Other serum lipoprotein classes gain alpha-T by exchange and transfer processes. We show here that the lipoprotein-free d > 1.22 g/ml fraction of human or pig serum increases the exchange rate of alpha-T by a factor of 2-4 as compared with spontaneous exchange/transfer. The alpha-T exchange/transfer (alpha-TET) activity was purified by multiple-step column chromatography. It gave a single band in PAGE with an apparent molecular mass of 75 kDa, and was found to be identical with the phospholipid transfer protein (PLTP). PLTP catalysed alpha-T exchange between different lipoprotein classes, as well as the transfer of alpha-T from artificial liposomes to high-density lipoproteins. The alpha-TET activity measured with a newly developed assay in ten healthy people was 2.45 +/- 0.88 nmol.ml-1.h-1.alpha-TET activity was negatively correlated with plasma low-density lipoprotein-cholesterol (r = -0.75; P < 0.01). It is concluded that human PLTP catalyses exchange/transfer processes of alpha-T between lipid compartments. This factor may be of relevance in atherogenesis and tumour initiation and growth.
Institute of Medical Biochemistry, University of Graz, Austria.
G M
GM
Kostner
K
K
Oettl
M
M
Jauhiainen
C
C
Ehnholm
H
H
Esterbauer
H
H
Dieplinger
D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D001798:Blood Proteins / Q000378:metabolism*; D002352:Carrier Proteins / Q000302:isolation & purification / Q000378:metabolism*; D053480:Cholesterol Ester Transfer Proteins; D004910:Erythrocyte Membrane / Q000378:metabolism*; D005215:Fasting; D005260:Female; D006023:Glycoproteins; D006801:Humans; D008074:Lipoproteins / Q000378:metabolism*; D008075:Lipoproteins, HDL / Q000378:metabolism; D008077:Lipoproteins, LDL / Q000378:metabolism; D008079:Lipoproteins, VLDL / Q000378:metabolism; D008081:Liposomes / Q000378:metabolism; D008297:Male; D008565:Membrane Proteins / Q000302:isolation & purification / Q000378:metabolism*; D049294:Phospholipid Transfer Proteins; D013439:Sulfhydryl Reagents / Q000494:pharmacology; D013552:Swine; D014810:Vitamin E / Q000378:metabolism*
D001798:Blood Proteins; C506642:CETP protein, human; D002352:Carrier Proteins; D053480:Cholesterol Ester Transfer Proteins; D006023:Glycoproteins; D008074:Lipoproteins; D008075:Lipoproteins, HDL; D008077:Lipoproteins, LDL; D008079:Lipoproteins, VLDL; D008081:Liposomes; D008565:Membrane Proteins; D049294:Phospholipid Transfer Proteins; D013439:Sulfhydryl Reagents; D014810:Vitamin E