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Studies on the enzymatic synthesis of cholesterol: Use of a liver acetone powder
Author(s) -
Scallen Terence J.,
Schuster M. W.,
Dhar A. K.,
Skrdlant H. B.
Publication year - 1971
Publication title -
lipids
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.601
H-Index - 120
eISSN - 1558-9307
pISSN - 0024-4201
DOI - 10.1007/bf02533030
Subject(s) - acetone , chemistry , sterol , microsome , chromatography , biochemistry , substrate (aquarium) , enzyme , ammonium sulfate precipitation , yield (engineering) , cofactor , cholesterol , biology , size exclusion chromatography , ecology , materials science , metallurgy
Abstract We have defined special conditions for the preparation of an acetone powder of rat liver microsomes which is capable of converting squalene to cholesterol in high yield. This preparation is also useful for the demonstration of cofactor requirements for certain reactions in sterol biosynthesis. Buffer washed acetone powders are virtually completely dependent upon the 105,000 × g supernatant of rat liver (S 105 ) for activity, yet S 105 by itself is inert in sterol synthesis. The ability of S 105 to stimulate sterol synthesis is heat liable, nondialyzable, trypsin sensitive, and has been partially purified by ammonium sulfate precipitation and chromatography on Sephadex G‐200. These results plus other experiments support the following hypothesis: the 105,000 × g supernatant of rat liver (S 105 ) contains a noncatalytic carrier protein (Sterol Carrier Protein or SCP) which originates from the endoplasmic reticulum, binds the substrate, and makes the substrate reactive to the sterol synthesizing enzymes present in the acetone powder of liver microsomes. The participation of SCP may be an important general mechanism in the biological synthesis of cholesterol.