Glial and neuronal localization of cerebroside-metabolizing enzymes

Abstract

Glial and neuronal cell preparations were made from young rat cerebrum and assayed for 3 enzymes involved in sphingolipid metabolism. A galactosyltransferase which makes galactocerebroside, a primary component of myelin, was found in all cell types examined, at fairly similar levels of activity. The same distribution of activities was found for the [beta]-galactosidase which hydrolyzes galactocerebroside. It is suggested that the very low levels of galactocerebroside found in neurons are the result of an inability of neurons to form the lipoidal cerebroside precursor, hydroxy ceramide, or a cerebroside-binding protein.The glucosyltransferase which makes glucocerebroside, an intermediate in ganglioside biosynthesis, was found only in neurons. This may be a new marker enzyme for neurons, in contrast to other brain cells. Since gangliosides are found in non-neuronal membranes, it appears likely that they (or some intermediate in biosynthesis) are transferred from neurons.