Pepsin protein hydrolysis

The present study indicates that the extracellular enzyme, pepsin, exhibits striking differences from its mammalian homologue with respect to optimum pH, Ea for catalysis, thermal stability, and substrate affinity. These data are interesting from the viewpoint of biological adaption at low temperatures, but they also provide some substance to our contention that enzymes from fish plant wastes can have sufficiently unique properties to justify their use over conventional sources of enzymes used as food-processing aids. The relatively low Eas for protein hydrolysis by fish pepsins indicate they may be especially useful for protein modifications at low temperatures. Alternatively, the poor thermal stability of the fish pepsins studied indicate that the enzymes can be inactivated by relatively mild blanching temperatures. The reality of this concept will have to await studies where the pepsins are used as food-processing aids. Such studies are currently underway in our laboratory. 

Specificity of Pepsin for Hydrolysis of Peptide Bonds in Proteins and Polypeptides ... 

Preparation of Bitter Peptides. The bitter peptides were prepared by hydrolysis of soy protein or com gluten with pepsin and hydrolysis of casein with trypsin. In the preparation of bitter peptides from soy protein, a 5% suspension of soy protein was hydrolyzed by pepsin [enzyme/substrate ratio = 1/100 (w/w)] at 37 C at pH... 

CHEMISTRY MECHANISM OF ACTION PHARMACOLOGY In the presence of acid-induced damage, pepsin-mediated hydrolysis of mucosal proteins contributes to mucosal erosion and ulcerations. This process can be inhibited by sulfated polysaccharides. Sucralfate... 

Hayashi and Kameda have reported 40% to 70% decreases in pepsin-catalyzed hydrolysis of lysozyme, soybean protein, casein and rlbonuclease A due to alkali-treatment under slightly milder conditions than ours (16, 29). Friedman, Zahnley and Masters reported an 80% decrease in digestibility of sodium hydroxide-treated casein measured as hydrolysis by trypsin (17). However, trypsin is specific for lysyl residues and lysine levels decreased to about half control values during the alkali-treatment, with a concomitant Increase in LAL formation. The somewhat lower digestibilities reported by these laboratories compared to our observations may be due to LAL formation in the proteins other than zein. 

Some of the earliest discovered enzymes were given names ending with -in to indicate their protein composition. For example, three of the digestive enzymes that catalyze protein hydrolysis are named pepsin, trypsin, and chymotrypsin. 

Carbohydrase-protease enzyme, protein hydrolysis protein hydrolysates Carbohydrase-protease enzyme, proteolytic food Pepsin Trypsin... 

Venison protein Hydrolysis with papain, pepsin, bypsin, a-chymo trypsin, alcalase, and neutrase Met-Gln-Ile-Phe-Val-Lys-Thr-Leu-Thr-Gly (APVPH I) and Asp-Leu-Ser-Asp- Gly-Glu-Gln-Gly-Val-Leu (APVPH 11). Kim et al. (2009)... 

Pish protein concentrate and soy protein concentrate have been used to prepare a low phenylalanine, high tyrosine peptide for use with phenylketonuria patients (150). The process includes pepsin hydrolysis at pH 1.5 ptonase hydrolysis at pH 6.5 to Hberate aromatic amino acids gel filtration on Sephadex G-15 to remove aromatic amino acids incubation with papain and ethyl esters of L-tyrosine and L-tryptophan, ie, plastein synthesis and ultrafiltration (qv). The plastein has a bland taste and odor and does not contain free amino acids. Yields of 69.3 and 60.9% from PPG and soy protein concentrate, respectively, have been attained. 

Since FPIAs are conducted as homogeneous immunoassays, they are susceptible to effects from endogenous fluorophores and from intersample variations. Such problems and others due to the sample matrix are largely avoided by sample dilutions of several hundredfold. Low-affinity, nonspecific binding of tracers to sample proteins, when present in sufficiently high concentrations, can result in a falsely elevated polarization signal. Interference from sample proteins can be eliminated when warranted, by proteolytic hydrolysis with pepsin.(46)... 

This aspartic proteinase [EC 3.4.23.22], from the ascomy-cete Endothia parasitica, catalyzes the hydrolysis of proteins with broad specificity similar to that of pepsin A, with preferential action on substrates containing hydrophobic residues at PI and PI. ... 

The question at once arose whether this a-pyrrolidine carboxylic acid, or a-proline as Fischer termed it in 1904, was a primary product or a secondary product formed by the action of mineral acids upon other products, but its formation by hydrolysis by alkali and by the action of pepsin followed by trypsin decided that it was a primary product and therefore one of the units of the protein molecule. Sorensen, in 1905, suggested that it might arise from an a-amino-S-oxyvalerianic acid which he synthesised, but the fact that this amino acid has not yet been obtained by hydrolysis of protein and the above facts seem to exclude this possibility. 

On-line hydrolysis of proteins catalyzed by trypsin or pepsin immobilized on monolithic silica beds was described by Kato et al. [86,195], whereas pepsin was encapsnlated into the silica-gel matrix (75 pm capillary column), without loss in enzymatic activity [195]. 

Pepsin. A general name for several names of the gastric juice that catalyze the hydrolysis of the protein to form polypeptides. 

Similarly, lysine has been incorporated into gluten hydrolyzate and lysine, threonine and tryptophan have been individually incorporated into zein hydrolyzates. Lysine, methionine, and tryptophan were incorporated simultaneously into hydrolyzates of protein from photosynthetic origin. A very interesting application of this procedure involved the preparation of low-phenylalanine plasteins from a combination of fish protein concentrate and soy protein isolate by a partial hydrolysis with pepsin then pronase to liberate mainly phenylalamine, tyrosine, and tryptophan, which were then removed on sephadex G-15. Desired amounts of tyrosine and tryptophan were added back in the form of ethyl esters and a plastein suitable for feeding to infants afflicted with phenylketonuria was produced. 

Hermansson et al. (36) used pepsin and papain to solubilize rapeseed protein concentrate. Papain had a lower solubilizing effect than did pepsin. However, the fact that pepsin has an optimum pH for activity at about 1.6, far below the pH range of most foods, made it possible to study the effects of controlled hydrolysis. At pH 7.0, all hydrolysates were more soluble than the original rapeseed protein concentrate. 

Figure 7. Emulsifying activity (expressed as volume percentage of the emulsified layer) of pepsin hydrolysates of soy protein as a function of pH and hydrolysis time. No hydrolysis (A) 2 h ( ) 8 h (X) 17 h ( ) 24h(O) (39).

You may have wondered how the proteolytic enzymes such as trypsin, pepsin, chymotrypsin, carboxypeptidase, and others keep from self-destructing by catalyzing their own hydrolysis or by hydrolyzing each other. An interesting feature of the digestive enzymes is that they are produced in an inactive form in the stomach or the pancreas—presumably to protect the different kinds of proteolytic enzymes from attacking each other or other proteins. 

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