Studies on cholesterol esterase in rat adipose tissue: comparison of substrates and regulation of the activity.
Efficiency of substrates for cholesterol esterase (EC 3.1.1.13) assay, and regulation of the activity were investigated in rat epididymal adipose tissue. The activity in the supernatant was activated by cyclic AMP-dependent protein kinase, cyclic AMP, ATP and Mg2+, both with micellar and liposomal substrates. However, the micellar substrate was more suitable for the assay than the liposomal with respect to Vmax and Km. Thus, the micellar substrate was employed. Pretreatment of the supernatant with exogenous cyclic AMP-dependent protein kinase enhanced the activity dose dependently, whereas that with cyclic AMP decreased the activity slightly. The cyclic AMP-dependent protein kinase activity in the assay mixture was within the range which can cause changes in cholesterol esterase activity. These results suggest that the amount of cyclic AMP-dependent protein kinase, rather than the cyclic AMP level, plays an important role in the regulation of cholesterol esterase in tissues with a high cholesterol esterase activity relative to the kinase activity, such as in adipose tissue.
Nakamura
K
K
University of Shizuoka, School of Pharmaceutical Sciences, Japan.
Inoue
Y
Y
Watanabe
N
N
Tomita
T
T
D000262:Adenylyl Cyclases / Q000378:metabolism; D000273:Adipose Tissue / Q000201:enzymology*; D000818:Animals; D002265:Carboxylic Ester Hydrolases / Q000378:metabolism*; D016048:Dideoxyadenosine; D015224:Dideoxynucleosides / Q000494:pharmacology; D004837:Epinephrine / Q000494:pharmacology; D005459:Fluorides; D006706:Homeostasis; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008297:Male; D010749:Phosphoprotein Phosphatases / Q000378:metabolism; D011188:Potassium / Q000494:pharmacology; D017680:Potassium Compounds; D011494:Protein Kinases / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D002787:Sterol Esterase / Q000378:metabolism*; D013379:Substrate Specificity; D013806:Theophylline / Q000494:pharmacology
D015224:Dideoxynucleosides; D017680:Potassium Compounds; D016048:Dideoxyadenosine; C033320:potassium fluoride; D013806:Theophylline; D011494:Protein Kinases; D002265:Carboxylic Ester Hydrolases; D002787:Sterol Esterase; D010749:Phosphoprotein Phosphatases; D000262:Adenylyl Cyclases; D005459:Fluorides; D011188:Potassium; D004837:Epinephrine