Identification of a distinct human high-density lipoprotein subspecies defined by a lipoprotein-associated protein, K-45. Identity of K-45 with paraoxonase

Eur J Biochem. 1993 Feb 1;211(3):871-9. doi: 10.1111/j.1432-1033.1993.tb17620.x.


In an attempt to provide immunological tools for subfractionation of high-density lipoproteins (HDL), monoclonal antibodies were raised against HDL complexes. Two clones identified a peptide, provisionally named K-45 (pI 4.5-4.9; molecular mass 45 kDa, range 42-48 kDa), whose plasma distribution and lipoprotein association were fully characterised. Gel filtration localised the peptide to the HDL region of human plasma where it co-eluted with apolipoprotein (apo) A-I, the structural protein of HDL. Complementary studies employing immunoabsorption with anti-(apo A-I) antibodies removed 90% of K-45 from plasma: conversely, anti-(apo A-II) antibodies eliminated only 10% of K-45. Immunoaffinity chromatography on an anti-(K-45) column revealed that the peptide was present in a distinct HDL subsepecies containing three major proteins: K-45, apo A-I and clusterin or apo J. The lipoprotein nature of the bound fraction was indicated by electron microscopy (diameter 9.6 +/- 3.3 nm) and quantification of lipids, the latter showing an unusually high triacyglycerol concentration. Plasma concentrations of K-45 were positively correlated with apo A-I and HDL-cholesterol and negatively correlated with apo B and total cholesterol. Thus, the peptide appears to be linked, directly or indirectly, to processes which give rise to an anti-atherogenic lipid profile. After completion of the present studies, an N-terminal sequence identical to that of K-45 was reported in recently isolated cDNA clones. These clones encode paraoxonase.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Apolipoprotein A-I / analysis
  • Aryldialkylphosphatase
  • Chemical Fractionation
  • Cholesterol, HDL / blood
  • Chromatography, Affinity
  • Chromatography, Gel
  • Humans
  • Immunosorbent Techniques
  • Isoelectric Point
  • Lipoproteins, HDL / blood*
  • Lipoproteins, HDL / chemistry
  • Molecular Sequence Data
  • Molecular Weight
  • Phosphoric Monoester Hydrolases / blood*
  • Phosphoric Monoester Hydrolases / chemistry
  • Regression Analysis
  • Ultracentrifugation


  • Apolipoprotein A-I
  • Cholesterol, HDL
  • Lipoproteins, HDL
  • Phosphoric Monoester Hydrolases
  • Aryldialkylphosphatase