Additive release upon degradation

Serpins form very tight complexes with their corresponding serine pro-teinases, thereby inhibiting the latter. A flexible loop region of the serpin binds to the active site of the proteinases. Upon release of the serpin from the complex its polypeptide chain is cleaved by the proteinase in the middle of this loop region and the molecule is subsequently degraded. In addition to the active and cleaved states of the serpins there is also a latent state with an intact polypeptide chain that is functionally inactive and does not bind to the proteinase. 

Many biological cells contain degradative enzymes (proteases) that catalyze the hydrolysis of peptide linkages. In the intact cell, functional proteins are protected from these destructive enzymes because the enzymes are stored in cell organelles (lysosomes, etc.) and released only when needed. The proteases are freed upon cell disruption and immediately begin to catalyze the degradation of protein material. This detrimental action can be slowed by the addition of specific protease inhibitors such as phenylmethyl-sulfonyl fluoride or certain bioactive peptides. These inhibitors are to be used with extreme caution because they are potentially toxic. 

In heated DMAc/LiCl, the keteniminium ions are generated in situ from the solvent. When the degrading agent was added externally in the form of a keteniminium precursor, cellulose degradation was even more pronounced. The thermolabile keteniminium precursor compound 4-(l-chloro-2-methyl-propenyl)morpholine (54) immediately releases keteniminium ions 55 upon thermal treatment (Scheme 22) [71]. Addition of the precursor in very small... 

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