Inhibition of fatty acyl desaturase by cyclopropene fatty acids.

Comparisons were made of the ratios of the specific activities of stearic acid to oleic acid in adipose tissue and liver triglycerides of rats given methyl stearate-lJ4C dissolved in 0.25 ml of corn oil and Sterculia foetida oil. The ratios were about 3 in the corn oil control animals compared to 31 to 43 in adipose tissue and 44 to 246 in liver triglycerides of the S. foetida test animals. When the labeled stearate was administered in 0.5 ml of S. foetida oil almost no label appeared in tissue oleic acid. The inhibition was also shown to be affected by sterculic acid in vitro with rat liver preparations. Evidence was obtained that the mechanism of inhibition is the irreversible binding of enzyme sulfhydryl groups by the cyclopropene group.