BIOSYNTHESIS OF LACTOSYLCERAMIDE BY RAT BRAIN PREPARATIONS AND COMPARISON WITH THE FORMATION OF GANGLIOSIDE GM1 AND PSYCHOSINE DURING DEVELOPMENT

Authors:
Publisher website
Google Scholar
Abstract
—This report deals with some properties of the enzyme from rat brain, which catalyses in vitro the formation of lactosylceramide, a probable precursor of the gangliosides, from UDP‐galactose and glucosylceramide. The enzyme is present in microsomes, mitochondria and synaptosomes, the latter having the highest specific activity, and appears to be firmly bound to the membranes of these particles. The enzymic activity is optimal at pH 6·8 and requires the presence of Mn2+.Lactosylceramide, the product of the reaction, was tentatively identified by its elution pattern from a Florisil column, its resistance to mild alkaline hydrolysis, thin‐layer co‐chromatography with authentic standards in six solvent systems, and location of the radioactivity in the galactose portion of the product obtained after incubation of labelled UDP‐galactose with unlabelled glucosylceramide and in the glucose portion after incubation of glucose‐labelled glucosylceramide with unlabelled UDP‐galactose.The activity of this enzyme, per unit of brain weight, was found to be highest at birth and to decrease gradually thereafter. A similar age distribution was observed for another galactosyltransferase, the one which catalyses the formation of ganglioside GM1 from Tay‐Sachs’ganglioside. In contrast, the activity of a third galactosyltransferase, which catalyses the formation of psychosine, and thus possibly is related to the increase of cerebrosides during myelination, is negligible during the first week and maximal about 20 days after birth.

This publication has 33 references indexed in Scilit: