Detoxification of oxidized LDL by transferring its oxidation product(s) to lecithin:cholesterol acyltransferase.
In the present study, we isolated modified LCAT (m-LCAT) by hydroxyapatite column chromatography after incubation of crude LCAT (after DEAE SephadexA-50 column chromatography, penultimate step of LCAT purification) with oxidized LDL (oxLDL) at 37 degrees C for 1 h. The activity was found to be about 30% lower than that of native LCAT (n-LCAT). When activity was determined in the presence of oxLDL, m-LCAT was less inhibited than n-LCAT by oxLDL. Treatments of purified LCAT either at 56 degrees C for 30 min, at 100 degrees C for 10 min, or with 6 mM 5-5' -dithiobis-2-nitrobenzoic acid or 9 mM diisopropyl fluorophosphates (each at 37 degrees C for 30 min) resulted in the loss of its cholesterol-esterifying activity. When examined for their ability to detoxify oxLDL, native LCAT and LCAT treated at 56 degrees C for 30 min were found to detoxify oxLDL. These results indicate that oxidation product(s) of LDL is transferred and bound to LCAT in a way that does not depend on its cholesterol-esterifying activity, but rather on the availability of the sulfhydryl group of cysteine residue and the hydroxyl group of serine residue.
Howlader
Zakir H
ZH
Laboratory of Nutrition, Graduate School of Agricultural Science, Tohoku University, 1-1 Tsutsumidori, Amamiya Machi, Aoba-Ku, Sendai 981-8555, Japan.
Kamiyama
Shin
S
Shirakawa
Hitoshi
H
Murakami
Yohei
Y
Ito
Michiko
M
Komai
Michio
M
Muramoto
Koji
K
Furukawa
Yuji
Y
D004791:Enzyme Inhibitors / Q000378:metabolism; D006801:Humans; D008077:Lipoproteins, LDL / Q000378:metabolism*; D010084:Oxidation-Reduction; D010455:Peptides / Q000032:analysis; D007862:Phosphatidylcholine-Sterol O-Acyltransferase / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D017392:Thiobarbituric Acid Reactive Substances / Q000032:analysis; D014357:Trypsin / Q000737:chemistry
D004791:Enzyme Inhibitors; D008077:Lipoproteins, LDL; D010455:Peptides; D017392:Thiobarbituric Acid Reactive Substances; C099252:oxidized low density lipoprotein; D007862:Phosphatidylcholine-Sterol O-Acyltransferase; D014357:Trypsin