On the biosynthesis of cerebrosides from 2-hydroxy acid ceramides: Use of deuterium labeled substrate and multiple ion detector

N (7′,8′,10′,11′,13′ ,14′,16′,17′-octadeutero 2′D-hydroxy docosanoyl) 4,5-dideutero D-erythro-trans sphingosine and N (2′D-hydroxy docosanoyl) 3-tritio D-erythro-trans sphingosine were prepared. A mixture of these ceramides was enzymically converted to cerebroside with mouse brain microsomes. The product was degraded to ceramides which were separated into molecular species by gas-liquid chromatography and analyzed by mass spectrometry. This analysis conclusively showed that the substrate was transformed into cerebroside and that there was no hydrolysis of the amide bond prior to galactosylation.