Stearic acid, cerebrosides

According to Klenk, the fatty acids bound covalently to the amino group of the sphingosine moiety consist mainly of stearic acid the sugars are D-galactose (as in the cerebrosides) and D-glucose. 

Cerebrosides synthesis can occur potentially by two routes 1) the acylation of psychosine to yield cerebroside, and 2) the galactosylation of ceramide. The acylation of psychosine can occur in vitro as demonstrated by Brady (1962) and suggested by the work of Cleland and Kennedy (1960). Brady prepared microsomes from the brains of young rats (14 day old sedimented at 3x10 g-min.). When these microsomal preparations were incubated in phosphate buffer (pH 7.8) with stearyl-l-i C-SCoA, Tween-20, magnesium chloride and ATP, incorporation into cerebrosides of the radioactivity in the stearic acid occurred in the presence of psychosine but not in the presence of sphingosine (unless UDP-glucose was present also). 

Cerebrosides have been isolated from Phycomyces blakeslearus (3), a fungus often found on animals dung, by extraction of mycelia with acetone and chloroform/methanol mixtures and purified on a silicic acid column, followed by a Florisil column. The bases obtained after hydrolysis were all phytosphingosine homologs ranging in length from C17 to C22. Palmitic,stearic, oleic, linoleic and hydroxy palmitic acids were the major fatty... 

The polar lipid fraction contains mainly sphingomyelins, whereas phosphati-dylethanolamines and phosphatidylcholines occur along with cerebrosides (ceram-idemono and diglucoside) only in very small amounts. Seventeen different EA are involved in the structure of the lipids in the neutral fraction of the shell, palmitic, stearic, and oleic acids predominate, and within the membrane, the proportion of linoleic acid is higher. The polar lipids in the cuticula and the membrane are very... 

Cerebrosides differ also in the composition of the constituent fatty acids. Alpha-hydroxy fatty acids with chain lengths ranging between 18 and 25 carbon atoms have been obtained from cerebroside hydrolysates. The saturated fatty acids most frequently found are stearic and lignoceric acids. The unsaturated fatty acids found mainly in cerebroside hydrolysates are 24 carbons long. Sphingosine is present in 95% of the cerebrosides, but cerebrosides containing dihydro-sphingosine have also been reported. 

The index of hydrolysis was the formation of ste (-l- C)-sph from cerebrosides containing stearic-1- C acid. The use of a detergent mixture containing sodium cholate was required for hydrolysis. The enzyme showed maximum activity at pH 4.5, at which point both the enzyme and cholate precipitated. Other substrates included naturally occurring cerebrosides (galactose containing) and showed the formation of ceramides containing normal and a-hydroxy fatty acid. Enzyme activity was seen also in rat brain, spleen, and kidney. 

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