Hydrolysis of glycoproteins

Alpenfels and coworkers studied the hydrolysis of glycoproteins and keratin fibers with 1 or 2 M hydrochloric acid for various periods of time at 100°. These investigators found that the concentration of neutral monosaccharides from hard keratin reached a maximum after hydrolysis with 2 M hydrochloric acid for 2 h at 100°, and the yield of the neutral monosaccharides was linear up to 25 mg of hair per mL of hydrochloric acid solution. The latter fact shows that a relatively large amount of protein does not interfere with the analysis of a relatively small amount of carbohydrate. 

Neeser and Schweizer introduced 4 M CF3CO2H for 1 h at 121° for hydrolysis of glycoproteins. Both neutral and amino sugars were considered. They compared this method to hydrolysis with 0.6 M hydrochloric acid for 4 h at 100° and 3 M hydrochloric acid for 0.75 h at 125°. Hydrolysis of fetal-calf-serum fetuin, bovine submaxillary mucin, and horse-radish peroxidase showed hydrolysis with CF3CO2H to be superior. 

Amino-sugars have been detected in the pmol range after condensation with 2-phthalaldehyde in the presence of 2-mercaptoethanol. Amino-acids also react yielding fluorescence intensities similar to those of amino-sugars. The products of acid hydrolysis of glycoproteins have been treated with 1-dimethyl-aminonaphthalene 5-sulphonyl chloride (dansyl chloride). The dansyl amino-... 

This support, which is of widespread use in the field of protein and DNA electrophoresis, is applied for the separation of oligosaccharides, labeled by fluoro-phores like 2-aminoacridone or 8-aminonaphthalene-1,3,6-trisulfonate, formed by enzymatic hydrolysis of glycoproteins. For this purpose small-pore gel material is used either with uniform pores or as... 

D-Galactose Hydrolysis of lactose. Can be changed to glucose in the liver and metabolized. Synthesized in the mammary gland to make the lactose of milk. A constituent of glycolipids and glycoproteins. Failure to metabolize leads to galactosemia and cataract. 

D-Mannose Hydrolysis of plant mannans and gums. A constituent of many glycoproteins. 1 ... 

A feasible way of introducing acid-stable linkages into carbohydrates is N-deacetylation. This can be achieved with hydrazine.59,70,71 The use of sodium hydroxide-sodium benzenethioxide in aqueous dimethyl sulfoxide for this purpose has also been described72 The difference in the acid hydrolysis of N-acetylhexosamine-con-taining carbohydrates before and after N-deacetylation was used in the study of complex glycoprotein saccharides from human erythrocyte membranes.73-75 Methylation analysis of the glycopeptides prepared... 

Acid phosphatase (acid phosphomonoesterase, EC 3.1.3.2) also catalyzes the hydrolysis of phosphoric acid monoesters but with an acidic pH optimum. It has broad specificity and catalyzes transphosphorylations. Acid phosphatases are a quite heterogeneous group with monomeric, dimeric, larger glycoprotein, and membrane-bound forms. Acid phosphatase activity is present in the heart, liver, bone, prostate, and seminal fluid. Prostate carcinomas produce large quantities of acid phosphatase, and the enzyme is, therefore, used as a biomarker [141]. 

Because of the numerous methods available for the hydrolysis of various glycoconjugates, including glycoproteins, mucins, glycosaminogly-cans, and gangliosides, it is useful to arrange these methods according to the type of acid employed. Some studies compared a particular method of... 

Enzymic hydrolysis is a useful tool for the identification of carbohydrate linkages, as well as for hydrolysis of the (labile) sialic acids. Neeser developed a method wherein the sialic acids are enzymically hydrolyzed and, simultaneously, enzymically converted into stable 2-amino-2-deoxymannose derivatives. This allows determination of carbohydrate constituents of glycoproteins in a single flask. 

A number of enzyme have been reported to catalyze the hydrolysis of glycosidic linkages in glycoproteins at N-acetylgalactosamine residues, exhibiting specificities at either the a- or the /3-linkage. Enzymes that are reported to act on both a- and /3-linkages have to be clearly characterized as to their specificity. 

This zinc-dependent endopeptidase [EC 3.4.24.11] catalyzes the hydrolysis of peptide bonds and exhibits preferential cleavage at the amino group of hydrophobic residues in proteins and polypeptides. Neprilysin is a membrane-bound glycoprotein that is inhibited by phos-phoramidon and thiorphan. 

Trichloroacetic acid is said to give better results with glycoproteins than either sulfuric acid or ion-exchange resins,51 and the solvent properties of 50% chloroacetic acid have been utilized in the hydrolysis of a p-toluenesulfonylated dextran.52... 

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