Journal of Lipid Research, Vol. 10, 326-330, May 1969
Copyright © 1969 by Lipid Research, Inc.
Evidence for separate monoglyceride hydrolase and triglyceride lipase in post-heparin human plasma
Heiner Greten , Robert I. Levy , and Donald S. Fredrickson
Molecular Disease Branch, National Heart Institute, National Institutes of Health, Bethesda, Maryland 20014
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.
Supplementary key words radioactive assay • lipoprotein lipase • inhibitors • hyperlipoproteinemia
Submitted on October 28, 1968
Accepted on January 27, 1969
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