PAF-acetylhydrolase activity on Lp(a) before and during Cu2+-induced oxidative modification in vitro
| dc.contributor.author | Karabina, S. A. P. | en |
| dc.contributor.author | Elisaf, M. C. | en |
| dc.contributor.author | Goudevenos, J. | en |
| dc.contributor.author | Siamopoulos, K. C. | en |
| dc.contributor.author | Sideris, D. | en |
| dc.contributor.author | Tselepis, A. D. | en |
| dc.date.accessioned | 2015-11-24T16:43:51Z | |
| dc.date.available | 2015-11-24T16:43:51Z | |
| dc.identifier.issn | 0021-9150 | - |
| dc.identifier.uri | https://olympias.lib.uoi.gr/jspui/handle/123456789/8745 | |
| dc.rights | Default Licence | - |
| dc.subject | paf-acetylhydrolase | en |
| dc.subject | lipoprotein (a) | en |
| dc.subject | apo(a) isoform | en |
| dc.subject | lysophosphatidylcholine | en |
| dc.subject | oxidation | en |
| dc.subject | platelet-activating-factor | en |
| dc.subject | low-density-lipoprotein | en |
| dc.subject | human-plasma | en |
| dc.subject | cholesterol acyltransferase | en |
| dc.subject | degrading acetylhydrolase | en |
| dc.subject | lipid-peroxidation | en |
| dc.subject | ldl | en |
| dc.subject | atherosclerosis | en |
| dc.subject | association | en |
| dc.subject | disease | en |
| dc.title | PAF-acetylhydrolase activity on Lp(a) before and during Cu2+-induced oxidative modification in vitro | en |
| heal.abstract | In human plasma with no detectable lipoprotein (a) (Lp(a)) levels, platelet-activating factor acetylhydrolase (PAF-AH) is associated with low density lipoprotein (LDL) and high density lipoprotein (HDL) with a distribution of 70 and 30%, respectively. We used a density gradient ultracentrifugation procedure to study the distribution of PAF-AH among lipoproteins in plasma containing Lp(a). Lp(a) was migrated as a broad band in the density region of d = 1.050-1.100 g/ml, independently of its isoform size. In plasma with Lp(a) levels 30-40 mg/dl or 80-100 mg/dl the PAF-AH activity migrated in this density region was 4 or 9% higher as compared to plasma having Lp(a) levels < 8 mg/dl (P < 0.05 or P < 0.02, respectively). Enrichment of plasma with the dense LDL(5) subfraction, significantly increased the enzyme activity distributed in this density region. The physicochemical properties of the Lp(a)-associated PAF-AH activity were similar to those reported for the LDL-associated enzyme. However, the kinetic constants in small Lp(a) isoforms were significantly higher compared to large ones. Isoform F had apparent K-m = 117 +/- 9 mu mol/l and V-max = 94 +/- 5 nmol/mg protein per min, and isoform S2/S3 had apparent K-m = 36 +/- 9 mu mol/l and V-max = 25 +/- 5 nmol/mg protein per min. Removal of apolipoprotein (a) (apo(a)) from Lp(a) by reductive cleavage with dithiothreitol, slightly affected the amount of PAF-AH existing on Lp(a) since, only 15 +/- 5% of the total enzyme activity dissociated from its particle after density gradient ultracentrifugation. During Cu2+-induced Lp(a) oxidation, the PAF-AH activity decreased from 10.90 +/- 2.30 nmol/mg per min to 2.57 +/- 0.56 nmol/mg per min 4 h after the initiation of the oxidation (P < 0.001). The apparent K-m of the enzyme remained essentially unchanged during oxidation, whereas V-max was significantly decreased from 58.6 +/- 7.8 nmol/mg protein per min to 38.2 +/- 8.7 nmol/mg protein per min (P < 0.03). An extensive hydrolysis of the endogenous phosphatidylcholine (PC) to lysophosphatidylcholine (Lyse-PC) was observed during Lp(a) oxidation, since the Lyso-PC/sphingomyelin molar ratio at the end of oxidation (0.55 +/- 0.09) was significantly higher than that beforeoxidation (0.19 +/- 0.01, P < 0.001). Our results show that the existence of Lp(a) in plasma alters the distribution of PAT-AH among the other lipoproteins. Apo(a) seems to affect the association of the enzyme with Lp(a) but does not bind itself to PAF-AH. During Lp(a) oxidation, the PAF-AH activity decreases whereas an extensive hydrolysis of the endogenous PC lu Lyse-PC is observed which is possibly due lo the PAF-AH activity. | en |
| heal.access | campus | - |
| heal.fullTextAvailability | TRUE | - |
| heal.identifier.secondary | <Go to ISI>://A1996UZ29800013 | - |
| heal.identifier.secondary | http://ac.els-cdn.com/0021915096058728/1-s2.0-0021915096058728-main.pdf?_tid=c82bb8a76a1ebee4dd095fcec15fe84f&acdnat=1333111332_ee6d8cc8314e1b7be68524ced6473867 | - |
| heal.journalName | Atherosclerosis | en |
| heal.journalType | peer reviewed | - |
| heal.language | en | - |
| heal.publicationDate | 1996 | - |
| heal.recordProvider | Πανεπιστήμιο Ιωαννίνων. Σχολή Θετικών Επιστημών. Τμήμα Χημείας | el |
| heal.type | journalArticle | - |
| heal.type.el | Άρθρο Περιοδικού | el |
| heal.type.en | Journal article | en |
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