Open Access

Differences between group X and group V secretory phospholipase A2 in lipolytic modification of lipoproteins

  • Shigeki Kamitani1, 2Email author,
  • Katsutoshi Yamada2,
  • Shigenori Yamamoto2,
  • Yoshikazu Ishimoto2,
  • Takashi Ono2,
  • Akihiko Saiga2 and
  • Kohji Hanasaki2
Cellular & Molecular Biology LettersAn International Journal201217:19

DOI: 10.2478/s11658-012-0019-2

Received: 2 December 2011

Accepted: 31 May 2012

Published: 13 June 2012

Abstract

Secretory phospholipases A2 (sPLA2s) are a diverse family of low molecular mass enzymes (13–18 kDa) that hydrolyze the sn-2 fatty acid ester bond of glycerophospholipids to produce free fatty acids and lysophospholipids. We have previously shown that group X sPLA2 (sPLA2-X) had a strong hydrolyzing activity toward phosphatidylcholine in low-density lipoprotein (LDL) linked to the formation of lipid droplets in the cytoplasm of macrophages. Here, we show that group V sPLA2 (sPLA2-V) can also cause the lipolysis of LDL, but its action differs remarkably from that of sPLA2-X in several respects. Although sPLA2-V released almost the same amount of fatty acids from LDL, it released more linoleic acid and less arachidonic acid than sPLA2-X. In addition, the requirement of Ca2+ for the lipolysis of LDL was about 10-fold higher for sPLA2-V than sPLA2-X. In fact, the release of fatty acids from human serum was hardly detectable upon incubation with sPLA2-V in the presence of sodium citrate, which contrasted with the potent response to sPLA2-X. Moreover, sPLA2-X, but not sPLA2-V, was found to specifically interact with LDL among the serum proteins, as assessed by gel-filtration chromatography as well as sandwich enzyme-immunosorbent assay using anti-sPLA2-X and anti-apoB antibodies. Surface plasmon resonance studies have revealed that sPLA2-X can bind to LDL with high-affinity (Kd = 3.1 nM) in the presence of Ca2+. Selective interaction of sPLA2-X with LDL might be involved in the efficient hydrolysis of cell surface or intracellular phospholipids during foam cell formation.

Key words

Secretory phospholipase A2 Low-density lipoprotein High-density lipoprotein Phospholipids Calcium ion

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