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Solubilization of rat liver microsomal cholesterol 7 α‐hydroxylase
Author(s) -
Hattersley Neil G.,
Boyd George S.
Publication year - 1975
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(75)80687-9
Subject(s) - george (robot) , citation , medical school , library science , chemistry , medicine , computer science , medical education , artificial intelligence
The 7 o-hydroxylation of cholesterol is considered to be the first and rate limiting step in the transformation of cholesterol to bile acids [ 1,2] . Cholesterol 7 o-hydroxylase (EC 1.14) is located in the microsomal fraction of rat liver and requires NADPH, molecular oxygen, and an electron transport system involving cytochrome P-450 and NADPH-cytochrome c oxido-reductase [3-71. When the concentration of bile acids in the enterohepatic circulation is lowered, either by cannulation of the bile duct or by feeding rats a bile acid sequestrant, the specific content of cytochrome P-450 remains constant, but the specific activity of cholesterol 7o-hydroxylase is increased 3-fold [ 1,3] . Cholesterol 7a-hydroxylase appears to be more sensitive to detergents and salts than other cytochrome P-450 dependent reactions [8]. It is therefore likely that the bulk of the liver microsomal cytochrome P-450 is not associated with cholesterol 7cr-hydroxylase activity. To study this enzyme in greater detail, it is first necessary to release it from the microsomal membrane. The mixed function oxidase system from rat liver microsomes has previously been solubilized and fractionated [9], but these methods rely on the detergency of sodium cholate or sodium deoxycholate. Since these detergents are both strong inhibitors of cholesterol 7a-hydroxylase it was necessary to explore other methods for the solubilization of this mixed function oxidase.