Papain properties

Finally, we come to enzyme models. D. W. Griffiths and M. L. Bender describe the remarkable catalytic property of certain cycloamyloses which act through formation of inclusion complexes, and in this respect recall the clefts containing the active sites in enzymes such as lysozyme and papain. 

Fractionation of Wheat Gluten Complete acid hydrolysis of the gluten results in loss of its deleterious properties. Deamidation by acid or by treatment with papain (K6) also markedly reduces its toxic action on patients with gluten-induced enteropathy. However, peptic/tryptic digestion does not significantly reduce toxicity (F27). This might be expected from the fact that... 

Soybean trypsin inhibitor, papain dl, and rubredoxin have identical topologies six strands of + 1,+ 1,+ 1,. . . proceeding to the left around the barrel if the chain termini are at the bottom. However, handedness is not nearly as meaningful a property for up-and-down topologies as it is for Greek keys, since up-and-down handedness can change on addition or delection of a single strand. 

Sekul et al. (29) studied the nitrogen solubility properties of enzyme-hydrolyzed peanut proteins. A deionized water dispersion of peanut flour (1 10, w/v) was treated with papain (0.5% total volume) at 45OC for 15 min. Solubility was tested over a range of pH 1 to 9. In general, papain treatment improved solubility at all levels examined except pH 2 and 8 (Figure 6). 

Pepsin and papain hydrolysates of rapeseed protein concentrate increased foam volumes and decreased drainage compared to the untreated control (36). Foaming properties could be further enhanced by adding a stabilizer such as carboxymethylcellulose. 

The Ca2+-dependent neutral proteases called calpains are found within the cells of higher animals. The 705-residue multidomain peptide chain of a chicken calpain contains a papain-like domain as well as a calmodulin-like domain.328 It presumably arose from fusion of the genes of these proteins. At least six calpains with similar properties are known.329 Some have a preference for myofibrillar proteins or neurofilaments.330 They presumably function in normal turnover of these proteins and may play a role in numerous calcium-activated cellular processes.331-3323... 

Scheme 4 Synthesis and photoisomerizable properties of azobenzene-functionalized papain.

In glycyl end (peptidase, however) the Gly-23 and Gly-65 of papain an replaced by Oiu and Aqg, respectively [45]. These residiies are located on the side walls of the active site cleft and can thus stericaly hinder the interactions al the Si subsite, which is oily accessible for Gly in glycyl endopeptidase. The absolute requirement for L-amino acids al Pi arises from the tact that when a peptide binds to the enzyme the hydrogen on the a-carbon points toward the enzyme On the vicinity of Gly-23) [63]. This is probably the reason why Domino adds cannot bind property (their side chain would clash with Gly-23) and why Gly is always conserved in position 23. 

A, K. Balls and R Linewcaver, Isolation and properties of crystalline papain. J. BioL E. F.lamen and A. K. Balk. Chymopapain a new crystalline proteinase from papaya... 

Plastein Formation. Plastein formation is another example of using proteases to modify high-protein food systems to drastically change the properties of that system (II). In the plastein reaction a protease such as papain is used to partially hydrolyze the proteins to about a 10,000-20,000-dalton size at a pH near neutrality. After concentrating the hydrolyzate to 35% (based on protein) and a change in pH, the same protease or a different one is used to catalyze the resynthesis of a few peptide bonds. This may result in a decrease in the solubility of the protein. 

Table I. Properties of a 20,000-Dalton Polypeptide Formed from Succinylated asi-Casein by Treatment with Papain in the Presence of L-Norleucine l-13C-Dodecyl Ester...

Table IV. Chemical and Functional Properties of Products Prepared from Gelatin0 by Papain-Catalyzed Attachment of L-Leucine ft-Alkyl Esters...

More recently, covalent chemical modification has been used as a powerful tool to enhance the functionality and stability of enzymes, for example, the covalent link of flavin to papain turned a protease into an oxido-reductase [107]. The use of this methodology was rekindled as a result of the explosion in the interest in commercial and synthetic applications of enzymes [108]. As a consequence, enzymes with new properties such as stability at extreme pH conditions, temperature, or solubility in organic solvents are being generated. 

An additional site for binding of SpA on the immunoglobulin molecules has been identified in the Fab portion. This property can easily be exploited for the separation of Fc fragments after proteolytic breakdown with papain (see Fig. 16 on page 581). This site has been demonstrated to be present in all... 

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