Enzymes medical/clinical applications

Several of these bioactive natural products have been successfully developed as therapeutics for clinical use. For example, Cyclosporin A is a fungal decapeptide principally used to suppress immune rejection in organ transplant patients. Mevinolin and compatin both control cholesterol synthesis in human. The search for enzyme- or receptor-targeted microbial products does not limit itself to medical use. Several commercially important antibiotics such as Nikkomycin and Avermectin have been found for agricultural applications in recent years. 

Blood-contacting materials have to fulfill particular requirements, as they are immediately exposed to all host defense mechanisms of the body. Thus, the contact of blood with foreign surfaces induces several cascade reactions and activation phenomena. These complex and highly interconnected reactions potentially create clinically significant side effects in the application of medical devices (e.g., cardiovascular implants, extracorporeal circulation, catheters) and interfere with the success of the medical treatments [64]. In certain cases, even the formation of thromboemboli or systemic inflammatory reactions were reported to occur as a consequence of the activation of coagulation enzymes and thrombocytes and/or the activation of the complement system and leukocytes (immune response) at the biointerfaces of the applied materials [65]. 

Enzymes may also be immobilized by microencapsulation. In this technique, which has medical applications, enzymes are enclosed by various types of semi-permeable membrane, e.g. polyamide, polyurethane, polyphenyl esters and phospholipids. Microcapsules of phospholipids are also called liposomes. The micro-encapsulated enzymes and proteins inside the micro-capsule cannot pass the membrane envelope, but low M, substrates can pass into it, and products can leave. Such encapsulated proteins do not elicit an antigenic response, and they are not attacked by proteases outside the microcapsule. They are therefore suitable for the delivery of enzymes for therapeutic purposes. This area of application is still at an early stage of development, but positive results have been reported from animal experiments and clinical studies, e.g. treatment of inherited catalase deficiency with encapsulated catalase. There are various methods of administration intramuscular, subcutaneous or intraperito-neal injection. However, their major area of application is outside the body. For example, microencapsulated urease can be employed as an artificial kidney in hemodiffusion (Rg.2). 

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