Isolation and partial characterization of an endogenous inhibitor of ceramide glycosyltransferases from rat brain.

A heat-stable factor has been extracted from the microsomal membranes of rat brain that inhibits the activities of rat brain ceramide galactosyl- and glucosyltransferases. It is nondialyzable, susceptible to proteolytic enzymes but resistant to DNase and RNase, and has no effect on lysosomal hydrolytic enzymes. The factor could also be prepared from microsomes of bovine, mouse, and rabbit brains and in much lower concentrations, from systemic organs of rats. This inhibitor might play a role in the regulation of ceramide glycosyltransferases in vivo.