Evidence for separate monoglyceride hydrolase and triglyceride lipase in post-heparin human plasma.
Post-heparin plasma contains an enzyme or enzymes with both triglyceride lipase (TGL) and monoglyceride hydrolase (MGH) activities. A simple and reproducible radioactive assay for measurement of MGH activity was developed and used, with a previously reported assay for TGL, to study lipolysis in plasma. After the injection of heparin, enzymatic activity against both tri- and monoglycerides appeared and disappeared from plasma at approximately the same rates. However, in contrast to TGL activity, MGH activity was: (a) much greater, (b) considerably less heat-sensitive, (c) unaffected by three inhibitors (NaCl, protamine, and pyrophosphate), (d) not influenced by radical changes in fat and carbohydrate content of the diet, and (e) normal in familial Type I hyperlipoproteinemia. The dichotomy between MGH and TGL activities in patients with genetic deficiency of TGL constitutes strong evidence that these are two different enzymes. The findings further indicate that when post-heparin lipolytic activity is measured for the purpose of detecting TGL deficiency, it may be necessary to perform the assay with a substrate free from partial glycerides.
D004032:Diet; D004040:Dietary Carbohydrates; D004041:Dietary Fats; D011756:Diphosphates; D005989:Glycerides; D006493:Heparin; D006801:Humans; D006867:Hydrolases / Q000037:antagonists & inhibitors / Q000097:blood*; D006949:Hyperlipidemias / Q000201:enzymology; D008049:Lipase / Q000037:antagonists & inhibitors / Q000097:blood*; D008074:Lipoproteins / Q000097:blood; D008722:Methods; D011479:Protamines; D012965:Sodium Chloride; D013696:Temperature; D014316:Tritium
D004040:Dietary Carbohydrates; D004041:Dietary Fats; D011756:Diphosphates; D005989:Glycerides; D008074:Lipoproteins; D011479:Protamines; D014316:Tritium; D012965:Sodium Chloride; D006493:Heparin; D006867:Hydrolases; D008049:Lipase