PAF-acetylhydrolase activity on Lp(a) before and during Cu2+-induced oxidative modification in vitro
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Ημερομηνία
Τίτλος Εφημερίδας
Περιοδικό ISSN
Τίτλος τόμου
Εκδότης
Περίληψη
Τύπος
Είδος δημοσίευσης σε συνέδριο
Είδος περιοδικού
peer reviewed
Είδος εκπαιδευτικού υλικού
Όνομα συνεδρίου
Όνομα περιοδικού
Atherosclerosis
Όνομα βιβλίου
Σειρά βιβλίου
Έκδοση βιβλίου
Συμπληρωματικός/δευτερεύων τίτλος
Περιγραφή
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.
Περιγραφή
Λέξεις-κλειδιά
paf-acetylhydrolase, lipoprotein (a), apo(a) isoform, lysophosphatidylcholine, oxidation, platelet-activating-factor, low-density-lipoprotein, human-plasma, cholesterol acyltransferase, degrading acetylhydrolase, lipid-peroxidation, ldl, atherosclerosis, association, disease
Θεματική κατηγορία
Παραπομπή
Σύνδεσμος
<Go to ISI>://A1996UZ29800013
http://ac.els-cdn.com/0021915096058728/1-s2.0-0021915096058728-main.pdf?_tid=c82bb8a76a1ebee4dd095fcec15fe84f&acdnat=1333111332_ee6d8cc8314e1b7be68524ced6473867
http://ac.els-cdn.com/0021915096058728/1-s2.0-0021915096058728-main.pdf?_tid=c82bb8a76a1ebee4dd095fcec15fe84f&acdnat=1333111332_ee6d8cc8314e1b7be68524ced6473867
Γλώσσα
en
Εκδίδον τμήμα/τομέας
Όνομα επιβλέποντος
Εξεταστική επιτροπή
Γενική Περιγραφή / Σχόλια
Ίδρυμα και Σχολή/Τμήμα του υποβάλλοντος
Πανεπιστήμιο Ιωαννίνων. Σχολή Θετικών Επιστημών. Τμήμα Χημείας