Proteolytic enzymes plant

Mammals, fungi, and higher plants produce a family of proteolytic enzymes known as aspartic proteases. These enzymes are active at acidic (or sometimes neutral) pH, and each possesses two aspartic acid residues at the active site. Aspartic proteases carry out a variety of functions (Table 16.3), including digestion pepsin and ehymosin), lysosomal protein degradation eathepsin D and E), and regulation of blood pressure renin is an aspartic protease involved in the production of an otensin, a hormone that stimulates smooth muscle contraction and reduces excretion of salts and fluid). The aspartic proteases display a variety of substrate specificities, but normally they are most active in the cleavage of peptide bonds between two hydrophobic amino acid residues. The preferred substrates of pepsin, for example, contain aromatic residues on both sides of the peptide bond to be cleaved. 

H. Murata, J. L. McEvoy, A. Chatterjee, A. Collmer, A. K. Chatterjee. Molecular cloning of an aepA gene that activates production of extracellular pectolytic, cellulolytic, and proteolytic enzymes in Erwinia carotovora subsp. carotovora. Mol. Plant Micr. Interact. 4 239 (1991). 

Peroxidase activity has long been associated with extracts of plant tissue and the crystalline enzyme from horse radish root has been studied in extenso, particularly in regard to its mechanism of action (11). Plants also contain ferredoxin and various specialized cytochromes, both of which substances play an essential role in photosynthesis (95, 96). Agavain, a crystalline proteolytic enzyme from the leaves of Agave,... 

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. 

Papain and Other Plant Sulfhydryl Proteolytic Enzymes A. N. Glaser and Emil L. Smith... 

Plant proteolytic enzymes are cysteine proteases, that is, they have a cysteine that is critical for the catalytic activity. Plant proteases are thought to function by a mechanism reminiscent of that shown for chy-motrypsin (fig. 8.11). Propose a structure for the acyl-enzyme intermediate that would exist for plant proteases. 

M. Sasaki, H. Yamamoto, H. Yamamoto, and 5. lida. Interaction of human serum proteinase inhibitors with proteolytic enzymes of animal, plant, and bacterial origin. J. Biochem. 75 171 119741. 

These examples illustrate the broad manner in which protease activity can impact the quality and processing of marine products. Another facet of this topic is that proteolytic enzymes from fishery wastes may find general use as aids in the processing of other foods and in nonfood applications. Millions of metric tons of fish offal, rich in digestive enzymes, presently are not used and present a serious, growing disposal problem in areas where fish meal plants are not located. The new northern cod fishery off the coast of Newfoundland will in itself provide an estimated 500,000,000 lb of offal by 1985. 

Proteolytic enzymes from animal, plant, and microbial sources currently are used extensively as food-processing aids. Generally, a given proteolytic enzyme has been chosen for a specific process or application based on empirical trials. In more recent years, with our better understanding of the properties of such enzymes, the choice has been made... 

Papain is a proteolytic enzyme from plants. In the HPLC assay developed to measure its activity, the water-soluble N-benzyl-L-arginine ethyl ester (B AEE) is used as the substrate. 

Papain and Other Plant Sulfhydryl Proteolytic Enzymes... 

Among the proteolytic enzymes, the plant proteases are the most widely used in the food industry. Most of the plant proteases which have been studied are characterized by a free sulfhydryl group which is essential for their activity. The most important of these so-called sulfhydryl or thiol proteases are papain, ficin, and bromelain. Since the literature on these enzymes has been the subject of several recent reviews (i, 2, 3, 4), major emphasis is placed in this presentation on the use of these enzymes in the food industry. Some of the more recent developments relating to the structure and function of the sulfhydryl proteases are discussed. 

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