Ceramide galactoside

Ceramide galactoside (galactose cerebroside) is the principal cerebroside present in the central nervous system and found in high concentration in the myelin sheath. This compound has been demonstrated to accumulate in the brain of patients with Krabbes disease (Austin, 1963). 

For some time these two reactions were believed to be entirely responsible for the biosynthesis of ceramide galactoside. It has been as-suin( d that ceramide giucoside is formed by a similar series of reactions where fJDP glucose substituted for UDP galactose. 

Recently an alternative pathway for ceramide galactoside synthesis has been described. This involves the ceramide-stimulated incorporation of galactose- C from UDP gaiactose- C into lipid (Basu el al., 1969 Morell and Radin, 1969 Fujino and Nakano, 1962), The reaction has been reported to occur in particles from mice, chick embryo, and rat brains. Only the hydroxy fatty acid.s containing eermnides are effective acceptors in the mouse and chick embryo system. These recent observations do not explain the mechanism by which the nonhydn>xy fatty acids containing ceramide galactosides are formed. 

V. Cerebroside Sulfate (Ceramide Galactoside 4-Sulfote, Sulfatide ... 

PAPS + ceramide galactoside - ceramide galactoside 3-sulfato + PAP... 

This reaction was described to occur in sonicated extracts of rat brain mierosomes (McKhann el al., 1965). The lipid acceptors were added as emulsions, and a detergent Brij 96 was present. Naturally occurring ceramide galactoside, as well as synthetic A -palmitoyI sphingosyl galac-toside, but not ceramide glucoside, stimulated the incorporation of from PAP S into a lipid which had properties of sulfatide. 

A more detailed publication has appeared recently in which sulfatide biosynthesis is described (Cumar et al., 1968). Sulfotransferase activity for ceramide galactoside was detected in all cerebral subceliular particles examined, including the soluble fraction. The bulk of activity was present in the crude mitochondrial portion, presumably in the synaptosomes. ilicrosomes exhibited the highest specific activity and a deoxycholate extract of these particles was examined more extensively. This prepara tion was employed principally for comparison of the sulfation of lactose and ceramide iactoside. An apparent K for ceramide galactoside varying from 3.3 to 8.5 X 10 M was reported. The product had chrnmatr raphic properties similar to sulfatide. 

This prepai ation does not possess the capacity to hydrolze ceramide galactoside. 

An inborn error of glycosphingolipid catabolism characterized by the accumulation of a ceramide derivative in blood and many tissues. It is due to a deficiency of one of the catabolic enzymes, a-D-galactoside galactohydrolase. It is transmitted by an X-linked gene. 

Hydroxy fatty acid) ceramide -f- UDP galactose — c mide galactoside... 

The i -galactosidase purified from rat brain which cleaves the galactoside bond in ceramide lactoside also posses.ses the ability to remove the terminal galactose moiety of monosiali anglioside (Gatt, 1967). 

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