Of hexosamines

IonPac KC-811 column separated the labile compounds N-acetylneuraminic acid and N-glycolylneuraminic acid released by mild acid hydrolysis of bovine vitronectin.245 Sialic acid is extremely labile to conditions of handling and must be released by mild acid hydrolysis.246 Derivatization with phe-nylisothiocyanate and separation by reversed phase chromatography was found useful in analysis of hexosamines from gastric mucosa.247 A review on separation of sugars and other carbohydrates which covers many important aspects is available.248... 

Boas, N. F. Method for the Determination of Hexosamines in Tissues. J. biol. 

Our present knowledge of the second type of hydrofuranol anhydro sugars, the 2,5-anhydro hexoses, is less extensive and definite than is the case with the 3,6-anhydro type. The credit for most of the information we have belongs to Levene and coworkers and results from the comprehensive study of hexosamines made by them. A good summary of this work was provided by Levene in 1921.49... 

When the ovalbumin was incubated with purified, jack-bean a-D-mannosidase, at least two molecules of D-mannose per molecule were released, suggesting that these residues are a-D-linked in a terminal position. Two glycopeptides having different contents of hexosamine were subjected to the action of purified 2-acetamido-2-deoxy-/ -D-glucosidase, and, in each case, two hexosamine residues per molecule were either inaccessible, or resistant to attack by the enzyme. 

Results of an experiment with an oligosaccharide free from amino acid were less conclusive, but were not incompatible with the structure shown. The oligosaccharide was prepared from a separated glycoprotein fraction having a D-mannose hexosamine ratio of 5 3. a-D-Mannosidase and 2-acetamido-2-deoxy-/3-D-glucosidase were used alternately. Initially, a-D-mannosidase removed about 1.5 D-mannose residues per molecule. Subsequent treatment of the residual oligosaccharide with 2-acetamido-2-deoxy-/3-D-glucosidase released rather less than one proportion of hexosamine residue, and then another 1.5 residues of D-mannose became open to attack by a-D-mannosidase. 

The per-O-acetylated 1-chlorides of hexosamines can be prepared by treating the hexosamine with an excess of acetyl chloride at elevated temperature.97 Under these conditions, acetylation of the hexosamine occurs at all positions except C-l, at which a chlorine atom... 

On the basis of the close correlation between the number of hydroxy-amino acids in bovine submaxillary mucin and the number of hexosamine and sialic acid residues, Hashimoto and Pigman (34) proposed that an O-glycosidic linkage was the only one that could be present in large amounts. Anderson et al. (38) reported a disappearance of much of the serine after incubation of the proteoglycan of chondroitin sulfate with alkali and suggested that this loss resulted from a -elimination reaction. 

Cornforth, J.W. and Firth, M.E. 1958. Identification of two chromogens in the Elson-Morgan determination of hexosamines. A new synthesis of 3-methylpyrrole. Structure of the pyrolene-phthalides . J. Chem. Soc. 1091-1099. 

Dische, Z. 1962. Color reaction of hexosamine. In Methods in carbohydrate chemistry, Vol. 1 (R.L. Whistler, and M.L. Wolfrom, eds.) pp.507-514. Academic Press. London. 

Figure 4. Selected ion monitoring of saccharide plus fatty acid ions of hexosamine-containing glycolipids from the same experiment as for Figure 3...

Much of this older work must be re-evaluated on the basis of availability of glycogen. A relationship to the adrenal-cortex secretion might be uncovered, but this is a possibility not yet explored. In man, the injection of adrenocorticotropic hormone (ACTH) has been reported not to influence the excretion of (endogenous) glucuronic acid or of hexosamine.176... 

Mode of synthesis A. cyanohydrin, by way of 2-nmino-2-deoxy-aldonic acid B. scission of sugar derivative epoxide with ammonia C. interconversion of hexosamine series D. hemihydrogenation of a-amino nitrile466 E. rearrangement of ketosyl-amine F. Removal of last carbon atom of hexosamine G. Hydrazinolysis (with inversion) of 2-0-tosyl-pentose. 6 Physical constants taken from this reference. c Derivatives (only) isolated. 

The presence of hexosamine in the hydrolyzate of a mucopolysaccharide may well be indicated on the basis of the above colorimetric tests and the amount present estimated. The identity of the amino sugar cannot thereby be established, since the colorimetric methods cannot differentiate between glucosamine, chondrosamine or any other 2-amino sugar. The ideal means for the identification of a hexosamine is the isolation of a well characterized crystalline derivative. Numerous compounds for this purpose or of potential application have been recorded in the literature but only in the case of the Schiff s bases have satisfactory results been obtained. 

Etzler and Kabat purified the agglutinating principle from Dolichos seed extracts by adsorption to insoluble polyleucyl hog A + H substance.108,517 Specific elution of the adsorbent with 2-acetamido-2-deoxy-D-galactose gave a protein that appeared homogeneous by immunodiffusion, immunoelectrophoresis, disc-gel electrophoresis under acid and alkaline conditions, and sedimentation analysis. The amino acid composition of the protein of molecular weight 141,000 reflected a high content of aspartic acid and serine, little methionine, and no cysteine. Carbohydrate analysis showed a sugar content of 2.4% of hexose, 1.6% of hexosamine, and 1.5% of 2-acetamido-2-deoxy-hexose. 

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