Cerebrosides solubility

Among the important glycolipids, which are combinations of carbohydrate and lipid, are the cerebrosides and gangliosides. These are constituents of brain and nervous tissue and are usually considered with lipids because they are water-insoluble. Water-soluble polymers of high relative molecular mass containing lipid and carbohydrate, known as lipopolysaccharides, are found in bacterial cell walls. 

Lipids are far more diverse chemically than other typical biomolecules such as amino acids, carbohydrates, and nucleotides. The definition of lipids includes simple fatty acids and their glycerol esters, sterols such as cholesterol, and phospholipids, sphingolipids, and cerebrosides. Lipids are generally defined by their common hydrophobic character, which makes them soluble in organic solvents such as chloroform. Virtually all lipids also have a hydrophilic group, which makes them surface active. 

The composition of milkfat is somewhat complex. Although dominated by triglycerides, which constitute some 98% of milkfat (with small amounts of diglycerides, monoglycerides, and free fatty acids), various other lipid classes are also present in measurable amounts. It is estimated that about 500 separate fatty acids have been detected in milk lipids it is probable that additional fatty acids remain to be identified. Of these, about 20 are major components the remainder are minor and occur in small or trace quantities (4, 5). The other components include phospholipids, cerebrosides, and sterols (cholesterol and cholesterol esters). Small amounts of fat-soluble vitamins (mainly A, D, and E), antioxidants (tocopherol), pigments (carotene), and flavor components (lactones, aldehydes, and ketones) are also present. 

The mechanically fragmented brain or spinal cord was dehydrated with acetone, as in the isolation of cerebrosides.7 Gangliosides are present in the water-soluble fraction they were recognized by color reactions (for example, Bial s orcinol reaction) based on the presence of sialic acid.159 The ganglioside mixture may be purified by partition... 

The activator of cerebroside sulfatase (or sulfatide activator ) was purified by Fischer and Jatzkewitz (1975) from human liver and identified as a water-soluble glycoprotein with an isoelectric point at pH 4.3 and a molecular weight of approximately 22,000 Daltons. From kinetic and binding experiments and from the fact that this cofactor stimulated only the degradation of lipid substrates but not of artificial water-soluble ones, these authors concluded that the cofactor serves to solubilize the lipid by binding to it and extracting it from the membrane (or micelle). The resulting activator/lipid complex was assumed to be the true substrate of the enzymic reaction (Fischer and Jatzkewitz, 1977, 1978). 

However, in the kidney the maximum incorporation had been attained 24 hours after injection, and the radioactivity was still present on the 32nd day. In the brain the 35S-substance sedimented with mitochondria in the kideny with microsomes and in the liver it was found in the soluble fraction. No cerebroside sulphate has been observed in rat blood cells or plasma. 

The distribution of soluble arylsulphatases in human tissues has been examined via ion-exchange chromatography. All tissues contained arylsulphatase A and B. In addition, brain singularly contained significant quantities of a minor anionic form (Bm) only trace amounts of Bm were found in liver, kidney, testis, and placenta. Arylsulphatases B and Bm had equal activity towards methylumbelliferyl sulphate, nitrocatechol sulphate, and UDP-2-acetamido-2-deoxy-D-galactose 4-sulphate, but both forms were inactive toward the arylsulphatase A substrates cerebroside sulphate and L-ascorbic acid 2-sulphate. The physicochemical properties of arylsulphatases B and Bm differed with respect to thermal stability, ionicity, and behaviour on polyacrylamide gel electrophoresis and isoelectric focusing. 

Cerebrosides are soluble in hot ethanol, chloroform-methanol-mixtures insoluble in ether and cold ethanol. They can be purified by recrystallization from acetic acid or chloroform-methanol or by chromatography on activated magnesium silicate (Florisil) (Radin et al. 1959). Alkaline hydrolysis of the peptide bond with barium hydroxide (Klenk 1926) results in the formation of psychosine partial acid hydrolysis yields ceramide ... 

The sulfatide isolated was soluble in chloroform-methanol (2—1) and failed to partition into an aqueous phase. Further identification of the sulfolipid was not made. Goldberg (1961) has postulated several pathways which may be involved in cerebroside sulfate synthesis. The initial steps are the activations of sulfate to 3 -phosphoadenosine-5 -phosphosulfate, i.e., PAPS, as described by Bandurski et al. (1956, 1958), Wilson and Bandurski (1956), and Robbins and Lipmann (1956, 1958a, b). 

A recent abstract and verbal report by McKhann, Levy, and Ho (1965) reports the in vitro synthesis of cerebroside sulfate by a microsomal enzyme system from young rat brain (18— 22 days old). Sonic irradiation of the microsomal fractions resulted in the solublization of a sulfokinase system. The complete synthesis required the microsomal fraction of brain, S04 , ATP, cerebrosides, and a non-ionic detergent (Bbij 96). The reaction reported would be consistant with equations 8, 9, and 10. No incorporation of S-sulfate into a cholesterol ester nor an exchange with unlabelled cerebroside sulfate was observed. 

In 1963, Mehl and Jatzkewitz succeeded in isolating fractions with cerebroside-sulfatase activity from pig kidneys, and Bleszynski and Dzialoszynski (1965) purified soluble arylsulfatases from ox brain. A study by Mehl and Jatzkewitz (1965) on the significance of a lack of arylsulfatase in ML as reported by Austin (1963 a), and Austin et al. (1964 a, b), with 2-hydroxy-5-nitrophenyl-sulfate as substrate, resulted in the finding of two fractions with arylsulfatase activity in normal kidneys. While in ML the smaller of both fractions was present in normal concentration, the second component, and the predominant one in normals, was below the limits (0.005 o. d. units Mehl and Jatzkewitz 1965) of the method in ML. It seems that diminution or lack of this heat-labile fraction, which corresponds to the arylsulfatase A of Austin, is typical for ML, and according to Mehl and Jatzkewitz (1965), supports the assumption of a block in the degradation of ML between sulfatides and cerebrosides (see fig. 3). 

D-Galactose is obtained from the hydrolysis of lactose, its chief source from raffinose from the galactans of gums and mucilages and from the galactolipides, or cerebrosides, of the central nervous system. It resembles glucose, but is much less sweet, and less soluble in water. It is dextro-rotatoiy, [a] = + 80°. On partial oxidation, it forms the sparingly soluble mucic acid, by which it may be identified. 

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