Proteins papain action

Industrial Uses. Papain is used in the leather industry to prepare the sides for tanning. Its proteolytic action removes some of the undesirable proteins which adhere to the hide and thus facilitates the subsequent tanning process. In the textile industry, the treatment of wool fibers with papain has been found to reduce the shrinkage from laundering. This appears to be caused by the abihty of the enzyme to destroy the elastic properties of wool protein. Because of its digestive action on protein, papain is used as a spot remover in the laundry and dry cleaning business. 

The conditions necessary Tor the plastein reaction have been reviewed by Fujimaki et al. ( ), and compared to those necessary for proteolysis by Arai et al. ( ). The substrate for the synthetic reaction must consist of low molecular weight peptides, preferably in the tetramer to hexamer range. These are usually produced from proteins by protease action. A number of proteolytic enzymes and protein substrates have been investigated for producing plastein reaction substrates. The most often used proteases are pepsin JJ), and papain (12,13), but others... 

Because of its wide specificity, papain will degrade most protein substrates more extensively than trypsin, pepsin, or chymotrypsin and its action is quite comparable to that of subtilisin (Hill and Schmidt, 1962 Nomoto et al., 1960a,b). Many free amino acids are liberated from proteins by papain, but it would not appear to produce as extensive hydrolysis as S. griseus protease (French et al., 1963). 

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. 

Three other plant enzymes, papain, bromelain, and to a lesser extent ficin, have found acceptance in the food industry as proteases. Papain is derived from the latex of the fruit, leaves, and trunk of Carica papaya, and bromelain from the fruit and stems of pineapple plants. These enzymes are used to prevent the hazing of beer when chilled (Chill-Proofing) by modifying the protein. Other applications for these plant proteases are in meat tenderizers and digestive aids. Ficin from the latex of Ficus carica is used to a much lower extent, perhaps because of its marked action on native protein and difficult handling. Proteases from Aspergillus Jlavus-oryzae, and to a lesser extent from Bacillus subtilis, have been used to replace and supplement these plant proteases in all applications, but papain continues to have the widest acceptance. 

Fig. 16. Action of papain on tosyl-L-arginine methyl ester at the various pH values indicated on the curves (100). The semiJogarithmic plot of 100 minus per cent hydrolysis against time shows that the kinetics are first order. The upper ordinate applies to the data at pH 4. The enzyme concentration at pH 6 was 0.0088 mg. of protein N per milliliter and at the other pH values was 0.0195 mg. of protein N per milliliter.

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