title: Lipoprotein-X.
abstract: Lipoprotein-X is an abnormal lipoprotein that appears in the sera of patients with obstructive jaundice, and thus is a sensitive indicator of cholestasis. In patients with familial plasma lecithin, Cholesterol acyltransferase (LCAT) deficiency, there is an inverse relationship between plasma Lp-X levels and LCAT activity. Ultracentrifugation procedures utilized for isolation of Lp-X have shown that it is associated with the low density lipoprotein fraction. Lp-X can be visualized by electrophoresis on either Agar or Agarose. The purity of Lp-X preparations has been documented by immunochemical procedures. The availability of highly purified antisera to Lp-X has served as a basis of one of the assay procedures for this lipoprotein. It's chemical composition has been established. Phospholipids and unesterified cholesterol constitute the bulk of the Lp-X molecule. Electron microscopic studies have demonstrated that Lp-X is a spherical particle which has strong aggregating properties. Membrane bound enzymes have been shown to aggregate with Lp-X. The fact that bile lipoprotein can be converted to Lp-X by the addition of albumin and that Lp-X can be converted to bile lipoprotein by the addition of bile salts offers a possible explanation for the origins of Lp-X. Phospholipases of plasma might play a role in the catabolism of Lp-X. The value and limitations of Lp-X determinations will also be addressed in this review.
mesh_terms: D000469:Alkaline Phosphatase / Q000378:metabolism; D000596:Amino Acids / Q000097:blood; D000818:Animals; D001059:Apoproteins / Q000097:blood; D001647:Bile Acids and Salts / Q000097:blood; D055598:Chemical Phenomena; D002621:Chemistry; D002779:Cholestasis / Q000097:blood* / Q000175:diagnosis; D002784:Cholesterol / Q000097:blood; D002788:Cholesterol Esters / Q000097:blood; D006801:Humans; D007158:Immunologic Techniques; D007863:Lecithin Cholesterol Acyltransferase Deficiency / Q000097:blood; D008073:Lipoprotein-X / Q000097:blood* / Q000302:isolation & purification / Q000502:physiology; D008074:Lipoproteins / Q000097:blood; D009708:Nucleotidases / Q000378:metabolism; D010743:Phospholipids / Q000097:blood; D011755:Pyrophosphatases / Q000378:metabolism; D012106:Research
chemical_list: D000596:Amino Acids; D001059:Apoproteins; D001647:Bile Acids and Salts; D002788:Cholesterol Esters; D008073:Lipoprotein-X; D008074:Lipoproteins; D010743:Phospholipids; D002784:Cholesterol; D009708:Nucleotidases; D000469:Alkaline Phosphatase; D011755:Pyrophosphatases