Plasma triglycerides in the form of chylomicrons and very low density lipoproteins (VLDL) are degraded in the extra-hepatic tissues (primarily muscle and adipose tissue) by the action of lipoprotein lipase (LPL). This enzyme, and a lipase of hepatic origin, hepatic triglyceride lipase (HTGL), whose function in lipoprotein metabolism is unclear, are released into the plasma following intravenous infusion of heparin. Although highly purified preparations of LPL and HTGL display similar molecular properties, the two enzymes differ markedly in a variety of characteristics that relate to their activity. This proposal outlines a series of experiments to define the structural and functional relationships between the two enzymes in humans and swine. As currently conceived, these studies include: 1. An investigation of the oligosaccharide components of the two enzymes; 2. Development of a radioimmunoassay for each enzyme; 3. Studies to determine the functional relevance of HTGL to lipoprotein metabolism; 4. Finnally, metabolic ward studies in humans with normal and aberrant lipoprotein metabolism will be conducted to detect and quantitate changes in the activity or mass of the lipase enzymes. In particular, Type I patients (i.e., those with hyperchylomicronemia) who have been shown to exhibit a deficiency in LPL will be studied by specific antibody techniques to determine the biochemical nature of the enzyme deficiency in this pathophysiological condition.