pharma matter: Novel Drug Delivery Systems
pharma matter: Novel Drug Delivery Systems: Introduction The method by which a drug is delivered can have a significant effect on its efficacy. Some drugs have an optimum ...
Pepsin
Pepsin terms a small group of gastric proteases that are active in acidic environments with a pH between 1 and 5. Its name comes from the Greek word pepsis, which means to digest. The most studied and commercially available form of pepsin is porcine pepsin A, isolated from the gastric mucosa of a pig. Pepsin is not directly formed after translation of its coding mRNA, but instead begins as a zymogen, or an inactive precursor. This preliminary, inactive form that is initially translated is called pepsinogen. The activation of pepsinogen is accomplished by lowering the pH below 4.5, which leads to a cascade of changes in bond structure, as shown in Figure 2 below, and yields the enzyme pepsin. The first step is reversable, however once the protein has progressed beyond step II, the protein cannot revert back to the inactive pepsinogen. (James and Sielecki, 1986) Figure . Proposed steps in the activation of pepsinogen into pepsin. Note that pepsin ends up with 44 amin...
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