Biosynthesis of brain sphingolipids and myelin accumulation in the mouse

Abstract

AbstractMicrosomal fractions were prepared from the brains of mice sacrificed at 13 are points between 5 and 48 days of age. Several enzymatic activities implicated in sphingolipid biosynthesis were assayed. The developmental pattern for the terminal step in galactosylceramide synthesis, transfer of galactose from UDP‐galactose to ceramide, peaked sharply at 17–19 days of age. Thus maximal activity for biosynthesis of this relatively myelin specific lipid appears slightly before the time period of maximal rate of accumulation of myelin (21–23 days). These latter data were obtained by isolating myelin from mice at 10 age points from 9 to 45 days of age. A control enzymatic activity, transfer of glucose from UDP‐glucose to ceramide to form glucosylceramide, was high at all age points with a broad peak between 20 and 35 days of age. Condensation of palmitoyl‐CoA and serine to form ketodihydrosphingosine, a common precursor to both glucosyl‐ and galactosylceramide also followed a developmental pattern of high activity at all age points, but peaked slightly at ca. 10–12 days of age.