Partial hydrolyzed peptides

TABLE 5 Amino Acid Composition of Partially Hydrolyzed Peptides (pp) and Polydisperse A -Acyl Arginine Peptides, in mols %... 

Elemental or peptide-based formulations have partially hydrolyzed protein or fat components. Peptide-based formulations replace some of the protein with dipeptides and tripeptides, thereby optimizing absorption in patients with impaired digestive or absorptive capacity. 

As already known, amino acids are the building units of peptides and proteins and they play an important plastic, energetic, and regulatory role in all living organisms. Almost all foods contain amino acids, either in the bound (partially hydrolyzed or intact proteins) or in the free form. High amounts of free amino acids can be found in some fermented foodstuffs as a consequence of proteolytic processes. 

Large peptides are partially hydrolyzed with enzymes (trypsin and chymotropsin) or acid to mixtures of di- and tripeptides. From the composition of these small units we establish the sequence of amino acids in the large polypeptide. 

Insulin was reacted with performic acid to cleave the disulfide bridges. Two polypeptides were isolated from this reaction, polypeptide A with 21 amino acids and polypeptide B with 30 amino acids. Polypeptide B was reacted with Sanger s reagent and then partially hydrolyzed. This produced a very complex mixture containing individual amino acids, dipeptides, tripeptides, and so on. All of the peptides that had the dinitro-phenyl group on their N-terminal amino acid were then isolated from this mixture. (This was relatively easy to accomplish because these labeled peptides have very different solubility properties from the unlabeled polypeptides in acidic solution.) The labeled peptides were separated by chromatography, and each component was hydrolyzed. The following results were obtained ... 

Plastein Formation. Plastein formation is another example of using proteases to modify high-protein food systems to drastically change the properties of that system (II). In the plastein reaction a protease such as papain is used to partially hydrolyze the proteins to about a 10,000-20,000-dalton size at a pH near neutrality. After concentrating the hydrolyzate to 35% (based on protein) and a change in pH, the same protease or a different one is used to catalyze the resynthesis of a few peptide bonds. This may result in a decrease in the solubility of the protein. 

Naturally the implication arose that there should be a high incidence of common peptides in the partial hydrolyzates of each of the serum proteins. This, of course, is the same implication that arose in Block s mind (3). Since 1956 this laboratory has been busy trying to isolate common peptides from each of the serum proteins as obtained from electrophoresis on starch slabs. In order to be able to prepare each of the protein hydrolyzates simultaneously we examined nonenzy-matic procedures and devised the dilute acid partial hydrolyzate method which has recently been described in detail (33, 34). In this method aspartic acid is preferentially eliminated from the peptide chain, the re-... 

After treatment with peroxyformic acid, the peptide hormone vasopressin is partially hydrolyzed. The following fragments are recovered. Propose a structure for vasopressin. 

A similar investigation was carried out by Kfirkela and Kulonen (1959) who partially hydrolyzed elastin by acids, alkalies, and enzymes under varying conditions and fractionated the products by adsorption on alumina and elution with ammonia. They obtained fractions in which the yellow color was enriched and determined the infrared and ultraviolet absorption spectra. They concluded that the yellow pigment was tightly bound to the peptide chain and that it did not appear to be a bile pigment. 

Linear polystyrene can be functionalized by various methods . The functional group capacity in these polymers diould not be too high otherwise, steric complications may arise. Poly(ethylene ycol) has been found to be most suitable for liquid-phase synthesis. This linear polyether and the block copolymers with functional groups at defined distances are chemically stable and soluble in a large number of solvents including water and can be precipitated selectively. Partially hydrolyzed poly(vinylpyrrolidone) and its copolymers with vinyl acetate were successfully applied in peptide synthesis. Poly(acrylic acid), poly(vinyl alcdiol), and poly-(ethylenimine) are less suitable for the sequential type synthesis because of the... 

The peptide or protein can also be partially hydrolyzed using endopeptidases. An endopeptidase is an enzyme that catalyzes the hydrolysis of a peptide bond that is not at the end of a peptide chain. Trypsin, chymotrypsin, and elastase are endopeptidases... 

The aromatic sulfonic acids, which were developed by Bergmann for the specific precipitation of amino acids, have also been used for the separation of peptides from a partial hydrolyzate of silk (Stein et al., 1944). 

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