Molecular Aspects of Hepatic Triglyceride Lipase and Lipoprotein Lipase from Human Post-Heparin Plasma
The intravascular catabolism and degradation of triglyceride-rich lipoproteins is correlated with glycerol ester hydrolizing activities, which are assumed to reside on the luminal surface of the capillary endothelial cells. One of these enzymes, lipoprotein lipase (LPL), has been found in several tissue homogenates, including adipose tissue, heart and mammary gland (Korn, 1955) as well as milk (Quigley et al., 1958). LPL is released from its membrane site by high molecular weight polyanions, in particular sulfated polysaccharides (Robinson, 1970). Shortly after intravenous heparin injection the activity is detectable in the plasma compartment. In recent years it has been demonstrated that postheparin lipolytic activities (PHLA) represent at least two major triglyceride hydrolyzing enzymes with a variety of others being present (La Rosa et al., 1972; Ehnholm et al., 1973; Greten et al., 1973). One of these is by kinetic criteria identical to LPL, the second is hepatic in origin and differs from LPL in not requiring a cofactor for full activity. In addition the hepatic triglyceride lipase (HTGL) is resistant to high salt concentrations and protamine in the assay medium (Ehnholm et al., 1973). However, although after heparin injection HTGL is released earlier and in larger quantities into the blood stream than LPL, exhibits greater stability and remains active much longer within the vascular bed.
KeywordsLipoprotein Lipase Sulfated Polysaccharide Plasma Compartment Glycerol Ester Performic Acid
Unable to display preview. Download preview PDF.