Identification and Some Characteristics of the Enzyme Protein of the Hormone-Sensitive Lipase from Rat Adipose Tissue

Abstract

A tri-, di-, and monoacylglycerol-hydrolyzing enzyme from rat adipose tissue has been detergent-solubilized and separated from monoacylglycerol lipase (H.Tornqvist and P.Belfrage, 1976, J. Biol. Chem. 251, 813–819) and lipoprotein lipase by use of ion-exchange chromatography, broad and narrow pH range electrofocusing and gel chromatography. The final preparation contained several different proteins. One of these, with an apparent minimum molecular weight of 86,000 by SDS-gel electrophoresis, was identified as the enzyme protein of hormone-sensitive lipase: a) the enzyme activity was reproducibly stimulated 50–100% by incubation With cyclic AMP-de­pendent protein kinase, cyclic AMP and ATP-Mg²⁺; b) the relative intensity of the Mw 86,000 protein band, and only this, closely paralleled the enzyme activity during narrow pH range electrofocus­ing and during subsequent gel chromatography of the electrofocusing enzyme peak fraction; c) only the Mw 86,000 protein extensively incorporated ³²P from [γ-³²P]ATP after incubation with protein ki­nase and cyclic AMP.

The pI of the enzyme was 6.7, it had the same Stokes radius on Sephadex G 200 as IgG and was 50% inactivated by 10 µM HgCl₂, 20 µM PCMB, 50 µM DFP, 10 mM NaF and non-ionic detergents above their critical micellar concentration.