Exogenous enzymes

Erythrocyte Entrapment of Enzymes. Erythrocytes have been used as carriers for therapeutic enzymes in the treatment of inborn errors (249). Exogenous enzymes encapsulated in erythrocytes may be useful both for dehvery of a given enzyme to the site of its intended function and for the degradation of pathologically elevated, diffusible substances in the plasma. In the use of this approach, it is important to determine that the enzyme is completely internalized without adsorption to the erythrocyte membrane. Since exposed protein on the erythrocyte surface may ehcit an immune response following repeated sensitization with enzyme loaded erythrocytes, an immunologic assessment of each potential system in animal models is required prior to human trials (250). 

CK catalyzes the reversible phosphorylation of creatine in the presence of ATP and magnesium. When creatine phosphate is the substrate, the resulting creatine can be measured as the ninhydrin fluorescent compound, as in the continuous flow Auto Analyzer method. Kinetic methods based on coupled enzymatic reactions are also popular. Tanzer and Gilvarg (40) developed a kinetic method using the two exogenous enzymes pyruvate kinase and lactate dehydrogenase to measure the CK rate by following the oxidation of NADH. In this procedure the main reaction is run in a less favorable direction. 

Endogenous and exogenous enzymes — While the role of (3-glucosidase affecting betalains is quite clear, the roles of polyphenoloxidase and peroxidase are less obvious. Betacyanin glycosides may be cleaved into the corresponding aglycones, the... 

Since a few years, new activities have been discovered in relation with fruit cell wall architecture, like new pectinases [1] (i.e. rhamnogalacturonase for the apple) new glycosidases [2](i.e. apiosidase for the grape). The improvement of the knowledge of fruit composition, cell wall chemistry, enzymology of endogenous and exogenous enzymes allow to supply the juice producers with preparations more and more purified and specific, blended in optimal combinations. 

Exogenous enzymes are used to produce fruit juices more easily during different stages of the process i.e. maceration, liquefaction or juice depectinisation These biochemical tools induce specific degradations that the processor can integrate into his process line to manage and valorize the fruits transformation into juice. 

Supplementation with pancreatic enzymes may reduce the pain and fatty diarrhea associated with chronic pancreatitis (Table 20-3). Best results are achieved in patients who have mild non-alcoholic pancreatic disease. Common pancreatic enzyme supplements contain lipase, amylase, and protease in varying proportions. Thus, the dose can be tailored to the patient s requirement for exogenous enzyme supplementation and response to therapy. 

Fig. 6.13. Schematic representation of a selective delivery obtained by antibody-directed en-zyme-prodrug therapy (ADEPT). An exogenous enzyme is coupled to a monoclonal antibody (mAb) targeted for tumor cells. In a second step, a prodrug is administered, which, as a selective substrate of the exogenous enzyme, will be selectively activated at the tumor site.

Fig. 6.14. Schematic representation of selective delivery obtained by gene-directed enzyme-prodrug therapy (GDEPT). The gene encoding an exogenous enzyme is transferred to tumor cells, where it is to be expressed. In a second step, a prodrug is administered that is selectively activated at the tumor site by the exogenous enzyme expressed by the tumor cells.

Crude enzyme preparations have been used in food processing since prehistoric times classical examples are rennets in cheesemaking and papaya leaves to tenderize meat. Added (exogenous) enzymes are attractive in food processing because they can induce specific changes, in contrast to chemical or physical methods which may cause non-specific undesirable changes. For some applications, there is no viable alternative to enzymes, e.g. rennet-coagulated cheeses, whereas in some cases, enzymes are preferred... 

The applications of exogenous enzymes in dairy technology can be divided into two groups ... 

Since the principal constituents of milk are proteins, lipids and lactose, proteinases, lipases and / -galactosidase (lactase) are the principal exogenous enzymes used in dairy technology. Apart from these, there are, at present, only minor applications for glucose oxidase, catalase, superoxide dismutase and lysozyme. Lactoperoxidase, xanthine oxidase and sulphydryl oxidase might also be included, although at present the indigenous form of these enzymes is exploited. 

The application of enzymes in food technology has been widely reviewed (Fox, 1991 Nagodawithana and Reed, 1993). Reviews on applications of exogenous enzymes in dairy technology include Fox and Grufferty (1991), Fox (1993) and Brown (1993). 

Fox, P.F. (1993) Exogenous enzymes in dairy technology-a review. J. Food Biochem., 17, 173-99. 

Exogenous enzymes, usually proteinases and/or peptidases. For several reasons, this approach has had limited success, except for enzyme-modified cheeses (EMC). These are usually high-moisture products which are used as ingredients for processed cheese, cheese spreads, cheese dips or cheese flavourings. 

Erythrocyte Entrapment of Enzymes. Erythrocytes have been used as carriers for therapeutic enzymes in the treatment of inborn errors. Exogenous enzymes encapsulated in erythrocytes may be useful both for delivery of a given enzyme to Ihe she of its intended function and for file degradalinn of pathologically elevuied. diffusible substances in the plasma. 

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