Side chain cleavage of some cholesterol esters

Area of Science:

• Biochemistry
• Steroid Metabolism

Background:

• Cholesterol sulfate side-chain cleavage by bovine adrenal mitochondria is known.
• The cleavage occurs without prior hydrolysis of the sulfate group.

Purpose of the Study:

• To investigate other cholesterol esters as substrates for the adrenal mitochondrial cleavage enzyme system.
• To further elucidate the mechanisms of cholesterol side-chain cleavage.

Main Methods:

• Testing various inorganic and organic cholesterol esters as substrates.
• Assessing the products of enzymatic cleavage.
• Evaluating the effects of cholesterol stearate, cholesterol phosphate, and digitonin on enzyme activity.

Main Results:

• Cholesterol nitrate, cholesterol phosphate, and acyl esters of cholesterol are cleaved to pregnenolone derivatives.
• Cleavage rate of acyl esters decreased with increasing acyl group size.
• Cholesterol stearate and cholesterol phosphate inhibited cleavage; digitonin inhibited cholesterol cleavage but accelerated cholesterol sulfate and nitrate oxidation.

Conclusions:

• The enzyme system cleaves various cholesterol esters without prior hydrolysis.
• Evidence supports the existence of multiple cholesterol side-chain cleavage enzyme systems in adrenal mitochondria.