Biochemical Engineering Fundamentals, Part 1 - Bailey J., Ollis D. 1989

Applications of Enzyme-Catalyzed Reactions
Applications of Hydrolytic Enzymes
Proteolytic Enzymes

There is A wide variety of Enzymes that selectively target nitrogen-containing compounds, particularly Proteins. These enzymes also find diverse Structure/179.html">Practical Applications. Like amylases, proteases are classified into enzymes that hydrolyze terminal groups (exopeptidases) and those that cleave internal peptide bonds (Endopeptidases).

Since enzymes, the essential catalysts of All living organisms, are themselves proteins, it is not surprising that proteolytic enzymes are often initially synthesized in an inactive form. The inactive form of an enzyme is either stored within The Cell or transported from its site of synthesis to the site where the active enzyme is required; in particular, the inactive forms of Pepsin, Trypsin, Chymotrypsin, and carboxypeptidase are transported within the cell. The activation of these proteolytic enzymes occurs via one of two pathways (Fig. 4.4). Interestingly, the activation of pepsin and trypsin is autocatalytic: the inactive enzyme precursor serves as a substrate for the active form, so the reaction yields more of the active enzyme. It is also noteworthy that once inactive trypsin or pepsin is converted into its active form, no further autocatalytic Cleavage of the enzyme is observed. The activation of the second group of enzymes, typically exopeptidases, requires ions of one or more specific metals. The standard METHOD FOR DETERMINING the metal ion requirements of enzymes and other cellular components involves studying changes in The activity of an enzyme solution during dialysis.

On an industrial scale, proteases are isolated from animal Tissues (Pancreas), higher plants (saps and latexes), as well as from Yeasts, Molds, and Bacteria. Some of these proteases and their applications are listed in Table 4.1.

Free proteases are primarily used in detergent formulation, dry cleaning, meat tenderizing, cheesemaking (rennin only), bating and tanning, silver recovery from photographic films and papers, The production of digestive AIDS, and in medicine for treating inflammatory processes and virulent wounds. Enzymes have been used as detergent additives since as early as 1913, but a particularly sharp increase in protease consumption for detergent production was observed in the late 1960s. Enzymes that facilitate the removal of proteinaceous stains are a blend of neutral and alkaline bacterial proteases, active in the pH range of 6.5 to 10.0 at temperatures from 30 to 60 °C. The production of enzymes for these purposes peaked in 1969, when 30–75% of all detergents in Western Europe and 40% in the US were formulated with enzyme additives. Subsequently, however, the US Federal Trade Commission expressed concern that such detergents might have adverse effects on human health, and in 1970–1971, the production of bacterial proteolytic enzymes dropped sharply. The subsequent lifting of the Federal Commission's warning and the Introduction of improved manufacturing Methods that minimize enzyme aerosol formation (through 'waxing') helped partially restore the demand for bacterial proteases in detergents. In 1980, approximately $6 million worth of such proteases were produced in the US.

a) From precursors:

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b) In the presence of Metal Ions:

FIG. 4.4. Activation of proteolytic enzymes: a — formation of active enzymes from precursors; b — formation of active enzymes in the presence of metal ions.

Various methods of tenderizing butchered meat carcasses using specific agents rely on the proteolytic activity of relatively inexpensive and heat-stable plant proteases, Papain and bromelain. The Aging process of whole carcasses is typically carried out prior to butchering and packaging via controlled autolysis at a Temperature of about 15 °C, combined with ultraviolet irradiation, which acts as a germicide to prevent the growth of undesirable microorganisms On the surface of the carcasses.

Crude pancreatic enzyme preparations from various animals contain all digestive proteases, including trypsin, as well as lipases and amylases. These mixtures, which possess potent hydrolytic activity, are used for dehairing animal hides and simultaneously hydrolyzing other non-collagenous proteins. Since pepsin also hydrolyzes Collagen (the fibrous protein that forms the structural basis of animal Skin), it cannot be used in leather Processing.

In the dairy industry, only one enzyme is widely used: rennin. Rennin cleaves a glycopeptide from soluble calcium caseinate, thereby converting it into relatively insoluble calcium paracaseinate, which precipitates as a curd. Other proteases can also convert calcium caseinate to paracaseinate; however, the proteolysis they catalyze usually does not stop there, and since the products of deeper casein degradation are more soluble, no curd forms under these conditions. The shortage of animal rennin has stimulated The Development of METHODS FOR PRODUCING analogous bacterial enzymes, and these are already used in cheesemaking. Genetic Engineering techniques are also employed to produce calf rennin using microorganisms.

Proteolytic enzymes are used in medicine and clinical practice as digestive aids and in the Treatment of severe wounds. Since enzymes are proteins, digestive enzymes are administered only in capsules that protect them from the acidic environment of The Stomach, which would inevitably cause their Denaturation. None of the enzymes listed in Table 4.1 are isolated from The Human Body. The administration of animal proteases to humans (porcine trypsin, for example, differs from human trypsin) is also used to suppress inflammatory processes in tissues; the HUMAN Immune Response is minimal when highly purified crystalline enzyme preparations are used. Unlike living Cells, dead cells are generally unable to protect themselves from the action of proteases. This difference underlies The Use of protease solutions for treating virulent or weeping wounds; proteases help soften necrotic tissue and cells, thereby facilitating wound drainage and accelerating healing.

Proteolytic enzymes, especially trypsin, suppress inflammatory processes and swellings associated with internal injuries and infections. Their action is likely based on dissolving Blood clots and extracellular protein deposits, on the local activation of other bodily defense systems performing the same Functions, or on both of these factors simultaneously. Proteolytic enzymes inhibit the progression of or completely cure several severe infectious diseases that lead to mucus accumulation in the Lungs.