Journal of Lipid Research, Vol. 10, 374-382, July 1969
Copyright © 1969 by Lipid Research, Inc.

The mechanism of heparin stimulation of rat adipocyte lipoprotein lipase

R. L. Patten and C. H. Hollenberg

The McGill University Medical Clinic, The Montreal General Hospital, Montreal, Quebec, Canada

Free fat cells and stromal-vascular cells were prepared from rat adipose tissue by incubation with collagenase. NH₄OH-NH₄Cl extracts of acetone-ether powders prepared from fat cells contained lipoprotein lipase activity but extracts of stromal-vascular cells did not. Intact fat cells released lipoprotein lipase activity into incubation medium, but intact stromal-vascular cells did not. The lipoprotein lipase activity of the medium was increased when fat cells were incubated with heparin, and this was accompanied by a corresponding decrease in the activity of subsequently prepared fat cell extracts. Heparin did not release lipoprotein lipase activity from stromal-vascular cells.

The lipoprotein lipase activity of NH₄OH-NH₄Cl extracts of fat cell acetone powders is increased by the presence of heparin during the assay. This increase is not due to preservation of enzyme activity, but to increased binding of lipoprotein lipase to chylomicrons. Protamine sulfate and sodium chloride have little effect on the binding of lipoprotein lipase to chylomicrons, but they inhibit enzyme activity after binding to substrate has occurred. These inhibitors do, however, inhibit the stimulatory effect of heparin on enzyme-substrate binding.

Supplementary key words enzyme—substrate binding • chylomicron—lipoprotein lipase binding • protamine sulfate • sodium chloride

Submitted on January 13, 1969
Accepted on March 25, 1969

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