Pronase, protein hydrolysis

Figure 7.14 shows how reactor productivity (g product/g enzyme) is affected by flux and enzyme concentration, for soy protein hydrolysis performed by Pronase enzyme. Maximum productivity can be obtained by operating the reactor at the highest flux and the lowest enzyme concentration. 

See Section IV.1 for alternative methods of chiral resolution. Partial chemical hydrolysis of proteins and peptides with hot 6 M HC1, followed by enzymatic hydrolysis with pronase, leucine aminopeptidase and peptidyl D-amino acid hydrolase, avoids racemiza-tion of the amino acids281. The problems arising from optical rotation measurements of chiral purity were reviewed. Important considerations are the nonideal dependence of optical rotation on concentration and the effect of chiral impurities282. 

For comparison, the solubility-pH profile of the deamidated protein was added to the plot containing the profiles for the pronase E-treated proteins (Figure 5). The deamidated protein, with 2.6% peptide bond hydrolysis, showed improved minimum solubility, comparable to the protein with 5.7% peptide bond hydrolysis and no deamidation. The shape of solubility-pH profile for the deamidated sample resembled that of the intact protein more than those of the pronase E-treated samples. For the deamidated sample, both the increase in solubility and the slight shift of minimum solubility to the acid side were the result of the increase in negative charges from deamidation. Obviously, deamidation was more capable of maintaining the original protein structure than proteolysis, which is essential for the development of desirable functional properties. 

In limited proteolysis, proteases such as pronase E hydrolyzed the 7S subunits of soy proteins more than the IIS subunits, resulting in enhanced protein solubility. Deamidation with relatively insignificant peptide bond hydrolysis that occurred during the germination of soybeans imparted to the storage protein improved solubility and emulsifying activity. On the other hand, the incorporation of phosphorus in soy proteins by the protein kinase cAMPdPK was too low to effect significant... 

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. 

Enzymatic gelation of partially heat-denatured whey proteins by trypsin, papain, pronase, pepsin, and a preparation of Streptomyces griseus has been studied (Sato et al., 1995). Only peptic hydrolysate did not form a gel. The strength of the gel depended on the enzyme used and increased with increasing DH. Hydrolysis of whey protein concentrate with a glutamic acid specific protease from Bacillus licheniformis at pH 8 and 8% protein concentration has been shown to produce plastein aggregates (Budtz and Nielsen, 1992). The viscosity of the solution increased dramatically during hydrolysis and reached a maximum at 6% DH. Incubation of sodium caseinate with pepsin or papain resulted in a 55-77% reduction in the apparent viscosity (Hooker et al., 1982). 

The authors of the studies cited above found that the enzymes used during sample preparation could not completely hydrolyze sample proteins into amino acids. This is partly understandable as both proteinase K and subtilisin are known to show hydrolyzing preference for specific residues of proteins. Accordingly, they do not necessarily arrive at total hydrolysis. At the same time, neither pronase E nor protease XIV could always provide 100 percent extraction of Se from the samples (see Table 19.1). Therefore, alternative methods should be developed in the field of sample preparation to replace enzymatic methods. 

Initial efforts by Noort et al. (1996,1997) to detect protein adducts of sulfur mustard focused on the 4-(2-hydrox-yethylthioethyl)-L-aspartate, 5-(2-hydroxyethylthioethyl)L-glutamate, the cysteine and the N-terminal valine adduct and two histidine adducts, Nl- and N3-(2-hydroxyethylth-ioethyl)-L-histidine, respectively. Acidic hydrolysis and pronase digestion were used to release these adducts from... 

Solubilization of Protein. Fish protein concentrate has high nutritional quality as determined both from its essential amino acid composition and from animal feeding experiments. Unfortunately, the concentrate is quite insoluble in water because of its denaturation by the solvent extraction method used in processing thus it contributes no functional properties to a food and must be used in bakery products primarily. A potentially useful method of solubilizing the protein is by proteolysis (9-12). As is the case with protein hydrolysates of casein and soybean protein, bitter peptides are formed during the hydrolysis. Papain and ficin produce more of these bitter peptides than does Pronase, for example (12). Pronase was found to produce a more brothy taste (13). A possible method of removing the bitter peptides is to convert the concentrated protein hydrolysate to plastein by further proteolytic enzyme action (14) to remove the bitter peptides. 

One of the current approaches to the improvement of the functional properties of proteins is enzymatic hydrolysis [148], The emulsifying ability of soy protein isolate can be increased by treatment with neutral fungal protease however, this treatment decreases emulsion stability [163], Partial hydrolysis of fish protein concentrate improves both emulsification and stability [164]. On the other hand, treatment of whey protein concentrate with pepsin, pronase, and pro-lase leads to a decrease in emulsification ability, suggesting that there... 

Kato et al. [54,55] reported using the proteases papain, pronase E, and chymotrypsin for the deamidation of food proteins, and Kato et al. [56] later reported deamidation of selected plant and animal proteins with chymotrypsin immobilized on controlled pore glass. The reactions were carried out at alkaline pH (pH 10) and 20°C and resulted in 5 to 20% deamidation with up to 8% peptide bond hydrolysis. Functional properties of proteins thus deamidated showed increased solubility and emulsifying and foaming properties. Enzymatic... 

Hydrolysis of whey protein concentrate (WPC) with pepsin, pronase or prolase decreased emulsifying capacity specific foam volume was increased by very limited hydrolysis (56,57), but decreased by more extensive hydrolysis, while foam stability was greatly decreased by limited hydrolysis (52) (Fig.3). 

Provansal and co-workers (15) treated sunflower protein Isolate with sodium hydroxide and observed formation of LAL, racemlzatlon of Isoleuclne and lysine (only these two were analyzed for racemlzatlon), and decreased vitro digestibility by pro-nase. While these workers suggested that the decreased pronase hydrolysis may have been due to crosslinking reactions, they also pointed out that It was likely that other amino acids were also racemlzed which could compromise the nutritional quality of the protein. 

Glutathione reductase has been purified. The protein contains flavin and sulfhydryl groups. The enzyme retains 10% of its activity after hydrolysis of 60% of the peptide bonds by pronase. 

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