Polysaccharides reactions with proteins

Hydrogen bonds, between carbohydrates and hydrophilic groupings of proteins of enzymes, V, 55 Hydrogen bromide, hydrolysis of polysaccharides with, II, 231 Hydrogen cyanide, reaction with osones, II, 80... 

Another commonly used reaction for insolubilization of proteins and ligands through amino groups to polysaccharides is with 2,4,6-trichlorotriazine [18,19]. This procedure is extensively used in our laboratories in the preparation of agarose immobilized enzymes. 

Periodate Oxidation mainly of polysaccharide supports has become a popular activation technique for protein immobilization [149]. Sodium periodate (Nal04) can react with vicinal cw-hydroxyl groups on cellulose, dextran, or any other diols to produce aldehyde groups. These aldehyde groups can easily be transformed into secondary amines by reductive oxidation or to hydrazides by reaction with dihydrazine. Further attachment of ligands or spacer molecules can be performed via primary amino groups. 

These interactions are frequently ionic in character. The coulombic forces of interaction between macroions and lower molecular weight ionic species are central to the life processes of the cell. For example, intermolecular interactions of nucleic acids with proteins and small ions, of proteins with anionic lipids and surfactants and with the ionic substrates of enzyme catalyzed reactions, and of ionic polysaccharides with a variety of inorganic cations are all improtant natural processes. Intramolecular coulombic interactions are also important for determining the shape and stability of biopolymer structures, the biological function of which frequently depends intimately on the conformational features of the molecule. 

Incorporating aldehydic fiinctions in a polysaccharide can be accomplished by reacting the polysaccharide with chloroacetaldehyde dimethyl acetal. After unmasking of the acetal, the modified polysaccharide is reacted with proteins by reductive amination [33]. Since the initial reaction of chloroacetaldehyde dimethyl acetal with polysaccharide lacks site-specificity, this method suffers from randomness as well as multiplicity of the attachment site on the polysaccharide. 

For historical reasons many pharmaceutical enzymes are assayed with physiological or biopolymeric substrates (proteins, polysaccharides, bacteria, oil emulsions), which causes a number of theoretical and practical problems. The interpretation of results is difficult when natural substrates are converted into products that are substrates themselves for the next enzymatic attack. Reaction rates often depend on the position of the scissile bonds in the molecule and the chemical nature of the moieties. Hydrolysis can proceed simultaneously on various bonds at various rates. In proteolysis it is assumed that some products are liberated only after denaturation and that during the reaction course new peptide bonds become accessible for hydrolysis. In these cases the enzymatic mechanisms become exceedingly complex, kinetic parameters are apparent values, and experimental results are strongly influenced by the reaction conditions. Reproducibility problems can occur upon assaying proteinases with a limited specificity for particular casein types. Bromelain and pancreatic proteinase, FEP pharmaceutical enzyme standards, are assayed with a casein substrate. The extent of soluble peptide release is a measure of proteolytic activity. However, due to limited specificity, some proteinases release peptides with a nonrandom aromatic amino acid composition. Contamination of casein preparations with protein and of test enzyme substances with other proteinases biases the assay results. Under these conditions, relative assay methods are indicated. 

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