Peptic hydrolysis

Peptic hydrolysis of ester derivatives of /3-casein and a-lactalbumin... 

Sitohy, M., Chobert, J.-M., and Haertle, T. 2001b. Peptic hydrolysis of methyl-, ethyl- and propyl-ester derivatives of (3-casein and a-lactalbumin. Milchwissenschaft 56, 303-307. 

Peptic Hydrolysis of Citraconylated and Decitraconylated Yeast Protein... 

Similar results as ours have recently been published by Zakar-ia and McFeeters (24). They studied the emulsifying activity of soy protein hydrolysates made by peptic hydrolysis and observed that with an increasing concentration of free amino groups in the hydrolysate the emulsifying activity exhibited an increase followed by a decrease. However, because of the differences in experimental conditions between their work and ours, a quantitative comparison would not be justified. 

Peptic Hydrolysis of Bonds Formed by the Aromatic Amino Acids in Human a- and -Chains... 

An additional factor that could limit peptic hydrolysis is the inhibitory effect of a free a-amino group adjacent to a potentially susceptible bond. It has been found that aeylated dipeptides are split more readily by pepsin than corresponding unprotected dipeptides. Thus, amino-terminal aromatic residues or leucine would not be released readily by pepsin. The lack of significant hydrolysis of the amino-terminal leucyl bond in the peptide shown in Fig. 3 might be the result of the inhibitory effect of the a-amino group. 

Fig. 3. Limited and extensive peptic hydrolysis of two tryptic peptides from human hemoglobin )8-chains (Goldstein et al., 1963). Peptide A contains residues 105-120 and peptide B contains residues 83-104 of the j8-chain.

A number of studies have been designed to determine the nature of the mechanism of proteolysis with a specific enzyme and substrate. Ginsberg and Schachman (1960a,b) concluded that chymotryptic hydrolysis of insulin probably proceeds by the all or none mechanism, whereas peptic hydrolysis of ribonuclease follows a zipper mechanism. 

Peptic hydrolysis was also applied [114] for food use with chicken heads. The final dried products were pale cream colored, had no bitter taste, were of high microbiological quality, and had a high mineral content. These highly soluble peptic hydrolysates would appear to be useful as flavoring and seasoning additives. 

After having been deprived of these three fractions, the liquid still contains albuminoid substances in solution, which can be diAdded into two new fractions. The first is precipitated when the liquid, previously saturated with anunonium sulphate, is addified the second remains in solution. We have, thus, definitely separated all the products of peptic hydrolysis into five portions. 

Products of peptic hydrolysis Products of tryptic hydrolysis (very advanced) Products of hydrolysis by the acids Products of hydrolysis by the alkalis Typical formation of plastein, with or -without gelatinization Mo formation of plastein Typical formation of plastein. -without gelatin ization Formation of plastein without gclatimza-tion Typical fonnation of plastein, without gelatmization Mo formation Formation of plastein -without ge-latinizatioa Mo formation... 

It appears from this table that Witte s peptone, the product of peptic hydrolysis of fibrin, contains still a very large quantity... 

At the beginning of this century, Sawyalow gave the name plastein to the insoluble material which appeared upon the incubation of a soluble mixture of enzymatic digestion products of fibrin with rennin (a pepsin-like enzyme from calf-stomach). This reaction, later observed also with enzymes different from rennin was studied more intensively in the 1920s by Wasteneys and Borsook [29] who showed that the products of peptic hydrolysis of egg albumin at pH 1.6 gradually formed a precipitate when the concentrated solution was incubated with pepsin at pH 4. 

At pH 3 the product from peptic hydrolysis of BSA was complex (Weber and Young, 9Ma,b Peters and Hawn, 1%7 Pearlman and Fong,... 

The production of three peptides, neokyrotiopin, VV-hemorphin-4, and brady-kinin-potentiating peptide, was monitored throughout the peptic hydrolysis of bovine hemoglobin using a 65-min 100/0- 33/67 (at 30 min)-> 23/87 wato- (0.1% TFA)/(60/40/0.1 acetonitrile/water/TFA) gradient. Peaks of interest were resolved and eluted in 30 min however, the elution of large peaks was seen imtil 60 min [1295],... 

Apart from the interaction between the side chains of the polypeptide substrate and the enzyme, there may be other interactions important for the efficiency of peptic catalysis. As was shown by Fruton t al. (11), if the methylene group in residue i is substituted for the carbonyl group, the substrate becomes an inhibitor. We found (12) that substitution of the -NH- group is residue P by an isosteric oxygen atom also resulted in a resistance to peptic hydrolysis. This compound was competitive inhibitor with Kj -K of the corresponding substrate (Table III). Therefore, formation of hydrogen bonds to the dipeptide region of the substrate is a prerequisite of peptic catalysis. 

While this chapter was in preparation, great strides were made toward the elucidation of amino acid sequence in hemoglobin and myoglobin. By using a skilful combination of tryptic and peptic hydrolysis of urea-denatured human Hb A, Braunitzer and co-workers [G. Braunitzer, N. Hilschmann, V. Rudloff, K. Hike, B. Liebold, and R. Muller, Nature 190, 480 (1961)] were able to fix the positions of about two-thirds of the amino acid residues in this protein. Similar amino acid sequence studies on sperm whale myoglobin by chemical analysis [A. B. Edmundson and... 

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