Protein enzyme modification

Chemical modifications of proteins (enzymes) by reacting them with iV-acylimidazoles are a way of studying active sites. By this means the amino acid residues (e.g., tyrosine, lysine, histidine) essential for catalytic activity are established on the basis of acylation with the azolides and deacylation with other appropriate reagents (e.g., hydroxylamine). 

Further, drug absorption, distribution, and elimination from the body may vary due to differences in protein binding, enzymic modification, etc, since proteins are also chiral entities (see Chapter 13). 

The following factors appear to control the emulsification properties of milk proteins in food product applications 1) the physico-chemical state of the proteins as influenced by pH, Ca and other polyvalent ions, denaturation, aggregation, enzyme modification, and conditions used to produce the emulsion 2) composition and processing conditions with respect to lipid-protein ratio, chemical emulsifiers, physical state of the fat phase, ionic activities, pH, and viscosity of the dispersion phase surrounding the fat globules and 3) the sequence and process for incorporating the respective components of the emulsion and for forming the emulsion. 

We have chosen to discuss enzyme modification of proteins in terms of changes in various functional properties. Another approach might have been to consider specific substrates for protease action such as meat and milk, legumes and cereals, and the novel sources of food protein such as leaves and microorganisms ( ). Alternatively, the proteases themselves provide categories for discussion, among which are their source (animals, plants, microorganisms), their type (serine-, sulfhydryl-, and metalloenzymes), and their specificity (endo- and exopeptidases, aromatic, aliphatic, or basic residue bond specificity). See Yamamoto (2) for a review of proteolytic enzymes important to functionality. 

Pallavicini et al. (16) utilized a-chymotrypsin immobilized on chitin to catalyze plastein formation from leaf protein hydrolyzates. When analyzed by gel exclusion chromatography, the products were comparable to those produced by soluble enzymes. Modification of Specific Functional Properties... 

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