Metabolism of fatty acids in rat brain microsomal membranes.

Using a technique in which substrate fatty acids are incorporated into microsomal membranes followed by comparison of their rates of desaturation with those of exogenous added fatty acids, it has been found that the desaturation rate may be greater for the membrane-bound substrate than for the added fatty acid. Moreover, the product of the membrane-bound substrate is incorporated into membrane phospholipid whereas the product of the exogenous substrate is found in di- and triacylglycerols and in free fatty acids, as well. These and other findings point to a normal sequence of reaction of membrane lipids with membrane-bounds substrates involving transfer of fatty acid from phospholipid to the coupled enzyme systems without facile equilibration with the free fatty acid pool.