Pepsin protein nature

Laufberger had tried to obtain the protein from horse liver, but it did not crystallize, and as he described to me when I met him in Prague some years ago, in those days everyone wanted to have protein crystals as a criteria of purity. Although James Sumner had crystallized jack bean urease in 1926, his preparations were somewhat impure, and it was only in the mid-1930s, when John Northrop and Moses Kubnitz showed that there is a direct correlation between the enzymatic activities of crystalline pepsin, trypsin and chymotrypsin that the protein nature of enzymes was generally accepted. 

The use of other acid proteases as substitutes for rennin in cheese making is determined by whether bitter peptides are formed during ripening of the cheese and by whether initial rapid hydrolysis causes excessive protein losses in the whey. Some of the acid proteases used in cheese making include preparations obtained from the organisms Endo-thia parasitica, Mucor miehei, and Mucor pusillus. Rennin contains the enzyme chy-mosin, and the scarcity of this natural enzyme preparation for cheese making resulted in the use of pepsin for this purpose. Pepsin and chymosin have primary structures that have about 50 percent homology... 

The digestion of heated or unheated soybean proteins by various enzymes is schematically compared with the nutritive values in Figure 18. Pattern A is typical of pepsin where, because of low pH of the reaction, the protein does not have to be denatured prior to addition to the reaction. Pattern B is typical of enzymes such as papain, bacterial neutral protease etc. where prior de-naturation of the substrate protein is required but there are no inhibitors of the enzyme present. Pattern C is typical of trypsin where prior heat treatment of the substrate protein is required to destroy inhibitors of trypsin as well as to denature the protein for digestion. The decrease in digestibility with prolonged heating in all three cases is due to modification of the substrate protein as described above. 

Solutions containing active enzymatic proteins (protease, lipase, trypsin, pepsin, prophase, or cellulase) or their mixtures, adjusted to the nature of the matrix of the solid material of biological origin [79, 83, 84]. The aim of the procedure is to break up proteins, polysaccharides, or fat chains and release the constituent amino acids, sugars, or short aliphatic chains. Enzymatic decomposition of the matrix can be considerably enhanced by application of ultrasound the process can, for example, increase the efficiency of disintegration of cell walls in yeast and thus improve the recovery of selenium by as much as 20 % [85]. 

This discussion of the metalloexopeptidases has focused on the general role of these enzymes in the conversion of dietary proteins into amino acids. In particular, the apparent synergistic relationship which the pancreatic carboxypeptidases have with the major endopeptidases, trypsin, chymotrypsin, and pepsin, in order to facilitate formation of essential amino acids has been stressed. The chemical characteristics, metalloenzyme nature, and mechanistic details of a representative of each class of exopeptidase have been presented. Leucine aminopeptidase from bovine lens was shown to be subject to an unusual type of metal ion activation which may be representative of a more general situation. Carboxypeptidase A of bovine pancreas was discussed in terms of its three-dimensional structure, the implications of x-ray crystallography to mecha ... 

Two experimental results indicate that there is an adsorption energy barrier related to the interfacial pressure. First, the presence of an energy barrier becomes evident only after an interfacial pressure of 0.1 mN m-1 is attained (Table II). In the second experiment, different compounds were spread at the air/water interface and the rate of adsorption of pepsin and lysozyme were measured under conditions where charge effects were minimized (MacRitchie and Alexander, 1963a). It was found that the rates of adsorption for these proteins were independent of the nature of the surface film and depended only on the surface pressure. 

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